All calculators

Addition & Subtraction for Kids

A hands-on game to add and take away objects and watch the numbers change.

Base Ten Blocks

Visual addition and subtraction with base ten blocks — see regrouping and borrowing step by step.

Butterfly Life Cycle for Kids

Follow the four stages of a butterfly: egg, caterpillar, chrysalis and butterfly.

Color Mixing Lab

Mix red, yellow and blue to make orange, green and purple, and learn primary and secondary colors.

Continents and Oceans

Tap the world map to discover the 7 continents and 5 oceans, hear their names and play a find-it game.

Division for Kids

Share objects into equal groups one by one, see the remainder appear and the division written out.

Fraction Pizza

Build, compare and find equivalent fractions by tapping slices of a pizza.

Gravity for Kids

Drop objects and watch gravity pull them down, and compare gravity on Earth, the Moon and other planets.

Greater Than, Less Than

Compare numbers with the hungry-crocodile game — pick greater than, equal to or less than.

Interactive Alphabet

Tap each letter to hear it, see a word that starts with it, and play the finding and ordering games.

Interactive Periodic Table

All 118 elements: tap one for its data and a real-world fact, filter by category or compare two.

Kids Calculator

A big, colourful, friendly calculator for children to practise the four basic operations.

Moon Phases

Walk through the 30 nights of the lunar month and watch all 8 phases change, plus a guessing game.

Multiplication for Kids

See multiplication as equal groups: 3 × 4 is three groups of four, and the times tables click.

Number Line

Visual addition and subtraction within 20 — a friendly frog hops each step.

Parts of a Plant for Kids

Tap the roots, stem, leaves and flower to learn what each part of a plant does.

Shapes for Kids

Learn 2D shapes: tap each shape to see its name and number of sides, then play a game.

Sink or Float Game

Predict whether each object will sink or float, drop it in the water and learn about density.

Skip Counting Game

Jump along the number line counting by 2s, 5s and 10s, see the pattern and try the quiz.

States of Matter for Kids

Explore solids, liquids and gases and heat or cool matter to watch it change state.

Telling Time

Learn to read an analog clock: drag the hands to explore, then take a leveled quiz.

Telling Time for Kids

Learn to read a clock: move the hands, read the time and play a set-the-clock game.

The Cell for Kids

Explore a cell like a tiny house: the membrane, nucleus, cytoplasm and what each part does.

The Solar System for Kids

Explore the Sun and its eight planets, from tiny Mercury to giant Jupiter.

The Water Cycle for Kids

Follow a drop of water through evaporation, condensation, precipitation and collection.

3D Dice Roller

Roll d4 to d100 as real 3D polyhedra that tumble and settle, with three visual styles.

3D Dice Roller

Tap to roll a real 3D die that tumbles and settles — fair and random every time.

Circle Area Calculator

Area, circumference and diameter from any one measurement.

Combined Probability Calculator

Enter several independent events and see the chance that all happen, that none do, and that at least one does.

Data Storage Converter

Convert data between KB, MB, GB, TB and binary KiB, MiB, GiB.

Decimal to Fraction Calculator

Convert any decimal into a fraction in lowest terms, including repeating decimals, with the steps shown.

Density Calculator

Solve density, mass or volume from the density formula.

Doubling Time Calculator

How long something takes to double at a steady rate — with the rule-of-70 estimate shown next to the exact answer.

Energy Converter

Convert energy between joules, calories, kilocalories, watt-hours, kWh and BTU.

Equation Solver

Type a linear, quadratic or two-variable equation and get the answer with the working shown.

Fraction Calculator

Add, subtract, multiply and divide fractions with fully simplified results.

Grade Calculator

Average, weighted average, GPA (4.0 scale), or the score you need on the final.

International Size Converter

Convert clothing and shoe sizes between US, UK, European and international systems.

Length Converter

Convert length between meters, kilometers, miles, feet, inches and more.

Password Generator

Strong random passwords in your browser, adjustable length and types.

Percentage Calculator

Percentages, discounts, increases and reverse percentages, solved instantly.

Random Number Generator

Random numbers by range or list, with or without repeats.

Scientific Calculator

Trig, logs, powers, roots and memory — the everyday scientific calculator, free in your browser.

Screen Size Comparison

Compare two screens by real surface area, not just diagonal inches, with a scaled visual.

Slope Calculator

Slope, line equation, angle and distance between two points.

Speed Converter

Convert speed between km/h, mph, m/s, knots and feet per second.

Speed, Distance & Time Calculator

Find speed, distance or time from the other two, with km/h and mph.

Statistics Calculator

Mean, median, mode, range and standard deviation of a list.

Strong Password Generator

Cryptographically strong passwords with a live strength rank and entropy meter.

Temperature Converter

Convert temperature between Celsius, Fahrenheit and Kelvin instantly.

Time Converter

Convert time between seconds, minutes, hours, days, weeks and years.

Time Zone Converter

The equivalent local time between two cities, with daylight saving handled for you.

Trigonometry Calculator

Sine, cosine and tangent of any angle, and the inverses to go the other way — in degrees or radians.

Unit Converter

Convert length, weight, temperature and volume, metric and imperial.

Volume Converter

Convert volume between liters, gallons, cups, tablespoons and more.

Weight Converter

Convert weight between kilograms, grams, pounds, ounces, stones and more.

Age Calculator

Your exact age in years, months and days from any date of birth.

Days Between Dates Calculator

Exact days between two dates, in weeks and years-months-days.

Time & Duration Calculator

Add or subtract hours and get exact durations between dates.

AI Token Cost Calculator

Estimate API budgets for GPT, Claude and Gemini from token usage.

Airbnb ROI Analyzer

Cash flow, cap rate and profitability scenarios for short-term rentals.

Auto Loan Calculator

Monthly payment, total interest and the full amortization table.

Break-Even Calculator

Units you must sell to cover costs, from fixed costs, variable cost and price.

CAGR Calculator

Compound annual growth rate between a starting and ending value.

Compound Interest Calculator

Project investment growth with compounding frequency and recurring contributions.

Compound Interest Simulator

An animated chart of your savings growing year by year, split into contributions and interest.

Debt Payoff Planner

Plan and animate paying off your debts with the snowball or avalanche method.

Debt-to-Income Calculator

Work out the two ratios lenders actually look at, and see how much debt you would need to clear to get inside the limits.

Discount Calculator

Final sale price and savings, with optional stacked discounts.

Future Value Calculator

What a single lump sum grows to over time at a given rate.

Inflation Calculator

Convert a US dollar amount from a past year into today's money, using the official CPI-U index.

IRR Calculator

Internal rate of return from an initial investment and a series of cash flows.

Live Salary Counter

Watch your pay tick up in real time — how much you earn per second, hour and day.

Loan Interest Rate Calculator

Find the interest rate from a loan amount, payment and term.

Margin Calculator

Sale price from a target margin, or margin and markup from cost and price.

Mortgage Calculator

Monthly payment, animated amortization chart, 28/36 affordability check and extra payment simulator.

Net Worth Calculator

Your net worth from total assets minus total liabilities.

Opportunity Cost of Military Spending

Translate a public spending figure into schools, hospitals, teachers, homes or scholarships — with the formula and sources shown.

Price Change Calculator

Percentage change between two prices, or apply an increase or discount to a price.

Refinance Calculator

Compare your current loan with a refinance: new payment, savings, break-even.

Rental Yield Calculator

Gross and net rental yield from price, rent and annual costs.

Retirement Calculator

Project your retirement pot from savings, monthly contributions and return.

Sales Tax & VAT Calculator

Add or remove sales tax, VAT, GST or IVA with an editable rate.

Savings Goal Calculator

How much to save each month to reach a target by a set date.

Savings Goal Date

The exact month and year you'll reach your savings goal, animated to the finish line.

Split the Bill by Dish

Split a restaurant bill by what each person ate — tax, tip and shared plates, with a clear total per person.

Subscription Cost Tracker

Add your subscriptions and see the real monthly and yearly total, with a bar for each.

Tip Calculator

Tip amount and total, with per-person bill splitting.

WACC Calculator

Work out the weighted average cost of capital, and see how much of it each side contributes once the tax shield is applied.

BMI & Calorie Calculator (TDEE)

Body mass index plus daily calories by activity level.

Calorie Deficit Calculator

Turn a daily calorie deficit into an estimated weekly weight loss.

Conception Date Calculator

Estimate the likely conception date from an estimated due date.

Daily Water Intake Calculator

Recommended daily water from your weight and activity level.

Macro Calculator

Split daily calories into grams of protein, carbs and fat.

Ovulation Calculator

Estimate your fertile window and ovulation day from your last period.

Pregnancy Due Date Calculator

Estimated due date and how many weeks pregnant, from your last period.

Sleep Cycle Calculator

The best times to wake up or go to bed, aligned to 90-minute sleep cycles.

Target Heart Rate Calculator

Max heart rate and fat-burn and cardio training zones by age.

VO₂ Max Calculator

Estimate your VO₂ max from a 12-minute run or your resting heart rate.

Asphalt Calculator

How many tons of hot-mix asphalt you need from the area and thickness of a driveway or lot, with a waste allowance.

BTU Calculator

Air-conditioner size (BTU) a room needs from area and conditions.

Concrete Calculator

Concrete volume and bags for slabs, columns, footings and DIY jobs.

Construction Materials Calculator

Convert between volume and weight for sand, gravel, cement, concrete, soil and more using each material's real density.

Countertop Area Calculator

Add up your countertop area section by section and get the square footage for marble, granite or quartz, with a waste allowance.

Paint Calculator

Litres of paint needed from wall area, coats and coverage.

Pool Volume Calculator

How many gallons or litres a pool holds — rectangular, round or oval — for dosing chemicals and sizing a heater or pump.

Room Size Calculator

Get a room's area in square metres and feet and see how it compares to average bedroom, living room and kitchen sizes.

Square Meters Calculator

Area from length and width, plus conversions between m², ft², and more.

Steel Weight Calculator

Weight of steel by profile — round bar, rebar, plate, I-beam, angle, tube — from its dimensions and length.

Wallpaper Calculator

Rolls of wallpaper needed from wall size, roll size and pattern repeat.

Water Tank Capacity Calculator

Volume in litres and gallons for rectangular and cylindrical tanks.

Freelance Hourly Rate Calculator

The hourly rate to charge based on your target income and the hours you can really bill.

Freelance Rate to Salary Calculator

Compare a freelance hourly or day rate to an employee salary — both ways — accounting for unpaid time, self-employment costs and benefits.

Pallet Calculator

How many cases fit on a pallet and how many pallets fit in a truck or container, from your box and pallet sizes.

Salary Converter

Convert a wage between hourly, daily, weekly, monthly and annual.

Severance Pay Calculator

Estimate severance from salary, years of service and an editable factor.

Take-Home Pay Calculator

Net pay from gross salary with an editable deduction rate.

Work Hours Calculator

Hours worked and overtime pay from your start, end and break.

Work Tenure Calculator

Your exact time employed in years, months and days, plus estimated accrued vacation.

Aperol Spritz Recipe Calculator

The classic 3-2-1 Aperol Spritz recipe scaled to any number of glasses, poured layer by layer.

Classic Margarita Recipe Calculator

The 2-1-1 classic margarita made from scratch — on the rocks or frozen — scaled to any number of glasses.

Cocktail Recipes

Six classic cocktails poured layer by layer, with exact amounts and the story behind each one.

Coffee Composition

Espresso, milk and foam poured layer by layer, in the real proportions of every coffee drink.

Coffee-to-Water Ratio Calculator

How many grams of coffee to use for your water, by method and ratio.

Espresso Martini Recipe Calculator

Vodka, coffee liqueur and espresso in exact measures, shaken with ice and scaled to any number of glasses.

Hugo Spritz Recipe Calculator

Prosecco, elderflower and soda in the exact 3-2-1 ratio, scaled to any number of glasses.

Interactive Pasta Recipe

Classic pasta recipes step by step, with servings that scale and a built-in cooking timer.

Kitchen Measurement Converter

Convert cups, tablespoons, grams, milliliters and more — by ingredient, so weight and volume match.

Meat Doneness Guide

Cooking time and doneness for beef, pork and chicken, with an animated cross-section of the cut.

Oven Temperature Converter

Convert oven temperatures between °C, °F and Gas Mark.

Recipe Calories & Macros Calculator

Total calories, protein, carbs and fat per serving from your ingredient list, with a macro split chart.

Recipe Cost Calculator

Total cost and cost per serving from your ingredient list, with a cost breakdown chart.

Recipe Scaler

Scale any recipe's ingredient quantities up or down by servings or a custom factor.

Rice to Water Ratio Calculator

The exact water for any amount of rice, by type — white, brown, basmati, jasmine — for stovetop, rice cooker or oven.

Roast Cooking Time Calculator

Roasting time from the weight and type of meat, with editable minutes per kg.

Scoville Scale

The heat of chili peppers in Scoville units, shown as a flame that grows with the spice.

Car Affordability Calculator

Maximum car price from your monthly budget, rate, term and down payment.

Car Depreciation Calculator

What a car will be worth after a few years, with a value chart.

Fuel Economy Calculator

Fuel economy in L/100km, km/L and MPG from distance and fuel used.

Lease vs Buy Calculator

Compare the total cost of buying versus leasing a car over the same term.

Trip Fuel Cost Calculator

Fuel cost of a trip from distance, consumption and fuel price.

Calories Burned Calculator

Calories burned by activity from your weight and duration (METs).

One-Rep Max Calculator

Estimate your 1RM from a set of reps, with training percentages.

Pace Calculator

Convert between running pace, time and distance.

Race Time Predictor

Predict your race time at any distance from a recent result (Riegel).

World Cup 2026 Players Countdown

From 1,248 players to 26 world champions: how the field shrank round by round, with every real result — Spain beat Argentina in the final.

Countdown Calculator

A live countdown to any date and time — days, hours, minutes, seconds.

Event Food Calculator

How much food to serve at an event from guest count and type.

Party Drinks Calculator

How much beer, wine and spirits to buy for a party, plus cocktail recipes scaled to your guests.

Wedding Budget Calculator

Estimate a wedding total from guests, catering, venue and extras.

4th of July Countdown

Live countdown to US Independence Day, with an animated flag. Rolls over to next year automatically.

Age Countdown Calculator

Your exact age in years, months and days, plus a live countdown to your next birthday.

Argentina Independence Day Countdown

Live countdown to the 9 de Julio, Argentina's Independence Day. Rolls over to next year automatically.

Black Friday & Cyber Monday Countdown

Live countdown to Black Friday and Cyber Monday. Rolls over to next year automatically.

Brazil Independence Day Countdown

Live countdown to the 7 de Setembro, Brazil's Independence Day. Rolls over to next year automatically.

Chile Fiestas Patrias Countdown

Live countdown to the 18 de Septiembre, Chile's national day. Rolls over to next year automatically.

Chinese New Year Countdown

Live countdown to the next Chinese New Year (Spring Festival). Rolls over each year automatically.

Christmas Countdown

Live countdown to December 25 with falling snow and a lit tree. Rolls over to next year automatically.

Colombia Independence Day Countdown

Live countdown to the 20 de Julio, Colombia's Independence Day. Rolls over to next year automatically.

Commonwealth Games 2026 Tracker

Countdown to Glasgow 2026 and a sortable medal table for the 74 competing nations.

Easter Countdown

Live countdown to the next Easter Sunday. Works out the moveable date automatically.

Father's Day Countdown

Live countdown to Father's Day by country. Pick your country and it adjusts to that date.

Halloween Countdown

Live countdown to Halloween, October 31. Rolls over to next year automatically.

Mexico Independence Day Countdown

Live countdown to the 16 de Septiembre, Mexico's Independence Day. Rolls over to next year automatically.

Mother's Day Countdown

Live countdown to Mother's Day by country. Pick your country and it adjusts to that date.

New Year Countdown

Live countdown to January 1 with days, hours, minutes and seconds. Rolls over automatically each year.

Thanksgiving Countdown

Live countdown to the fourth Thursday of November. Recalculates the date and rolls over each year.

Tour de France 2026 Tracker

Which stage the race is on, how many are left, and the kilometres covered and remaining.

Valentine's Day Countdown

Live countdown to Valentine's Day, February 14. Rolls over to next year automatically.

Baby Name Generator by Numerology

Baby name ideas whose numerology number, with your surname, matches a quality you pick.

Big Number Calculator

Turn huge amounts of time into a real date from today.

Binge-Watch Calculator

How many hours and days it takes to binge a whole series.

Celebrity Net Worth Calculator

The estimated fortune of famous people, compared to your own income.

Chinese Gender Predictor

Boy or girl? The traditional Chinese method from the mother's age and conception month.

Chinese Zodiac Calculator

Your Chinese zodiac animal and element from your birth year.

Daily Number Puzzle

Reach 24 using four numbers and + − × ÷ — a fresh brain teaser every day.

Day of the Week Calculator

What day of the week any date fell on, plus how many days ago.

Dice Probability Calculator

The exact odds of rolling any total with any number of dice and sides.

Hail Mary Interstellar Travel

How long to reach the stars of Project Hail Mary — Tau Ceti and Erid — at different speeds, with an animated ship.

Interplanetary Travel

Pick a planet and a speed, then watch a ship make the trip — the time reveals on arrival.

Lottery Odds Calculator

Your real odds of winning a lottery jackpot from the pool size and picks.

Name Compatibility Calculator

The classic FLAMES name game — enter two names and reveal the relationship.

Numerology Calculator

Life Path, Destiny and Soul numbers from your birth date and name.

Reading Time Calculator

How long a text takes to read from its word count and reading speed.

Relationship Calculator

How long you've been together, in years, months and days, with your next anniversary.

Screen Time in Perspective

See what your daily screen time adds up to over years — in movies, books and more.

Space Travel Time Calculator

How long to reach the Moon, Mars or the stars at any speed.

Special Birthdays Calculator

Find the dates of your milestones: your 10,000th day alive, your billionth second, your golden birthday and more.

Your Age on Other Planets

How old you'd be on Mercury, Mars or Neptune, with an animated solar system.

Zodiac Compatibility Calculator

Zodiac signs of two dates and an element-based compatibility score.

Aquarium Size Calculator

Fish tank volume in litres and gallons, plus a stocking guide, from its dimensions.

Cat Age Calculator

Convert your cat's age to human years with the standard feline chart.

Cat Food Calculator

Estimate how much to feed your cat from its weight, life stage and food.

Cat Pregnancy Calculator

Your cat's likely kittening due date from the mating date, with the normal range.

Chickens for Eggs Calculator

How many hens you need for the eggs you want each week.

Dog Food Calculator

Estimate how much to feed your dog from its weight, life stage and food.

Dog Pregnancy Calculator

Your dog's likely whelping due date from the mating date, with the normal range.

Dog Years Calculator

Convert your dog's age to human years by size, with the science-based estimate too.

Horse Age Calculator

Convert your horse's age to human years with the standard equine chart.

Litter Box Calculator

Find how many litter boxes you need with the one-per-cat-plus-one rule.

Rabbit Age Calculator

Convert your rabbit's age to human years with a simple estimate.

Atomic Structure Simulator

Build an atom and see its protons, neutrons and electron shells: the Bohr model and electron configuration.

Chaos Lab — Lorenz Attractor & Double Pendulum

Two classic chaotic systems: the Lorenz attractor and the double pendulum, showing the butterfly effect live.

Chemical Equation Balancer & Stoichiometry Calculator

Balance any chemical equation and run stoichiometry: molar masses, mole ratios and the limiting reagent.

Combined Gas Law Calculator

Leave any one of the six values blank and it solves for that one, converting units and checking the physics as it goes.

Concave & Convex Mirror Simulator

Ray-tracing simulator for concave and convex mirrors, with the mirror equation and magnification.

Coulomb's Law Calculator & Electric Field Simulator

Electrostatic force between point charges and the electric field they create, with the CODATA Coulomb constant.

Crosswind & Headwind Component Calculator

Resolve wind into crosswind and headwind/tailwind components for any runway, with the vector geometry.

Density Altitude Calculator

Density altitude from elevation, altimeter setting and temperature, using the ICAO Standard Atmosphere.

Gravity Simulator — N-Body Lab

An interactive N-body gravity sandbox: place masses, launch them and watch orbits form under Newtonian gravity with Velocity Verlet integration.

Hardy-Weinberg Equilibrium Calculator

Genotype and allele frequencies under Hardy-Weinberg equilibrium (p² + 2pq + q² = 1), with a chi-square test.

Hohmann Transfer Orbit Simulator

The two burns, total delta-v and transfer time of a fuel-optimal Hohmann transfer, from the vis-viva equation.

Ideal Gas Law Calculator (PV = nRT)

Solve PV = nRT for pressure, volume, moles or temperature, with the exact 2019 SI gas constant.

Moment of Inertia Calculator

Moment of inertia of rods, disks, cylinders, spheres and hoops about any axis, with the parallel-axis theorem.

Monte Carlo Risk Simulator

Run a Monte Carlo simulation over uncertain inputs for the full distribution of outcomes: mean, P10/P50/P90 and risk.

NPV, IRR & Payback Calculator

Net present value, internal rate of return, payback and discounted payback from a stream of cash flows.

Prism Light Dispersion Simulator

See a prism split white light into a rainbow: refraction, Snell's law and dispersion.

Projectile Motion Calculator

Range, maximum height and time of flight of a projectile from launch speed and angle, with the trajectory.

Punnett Square Calculator

Enter two parent genotypes and get the square drawn out, with the genotype and phenotype ratios worked through.

RLC Circuit Simulator

Frequency response of a series RLC circuit: resonant frequency, quality factor Q and bandwidth, plotted live.

Rotational Kinetic Energy Calculator

Energy stored in a spinning object, from its moment of inertia and how fast it turns — with common shapes built in.

Simple Pendulum Calculator

Period and frequency of a simple pendulum from length and gravity, with the large-amplitude correction.

Snell's Law Calculator

Find the refracted angle from the incident angle and the two materials — with the critical angle and total internal reflection handled.

Spacetime Curvature Simulator

A visual analogy of how mass curves spacetime in general relativity, with test particles bending along geodesics.

Special Relativity Calculator

Lorentz factor, time dilation, length contraction and relativistic energy for any speed, with the exact speed of light.

Spring-Mass Oscillator Calculator

Period, frequency and energy of a mass on a spring: simple harmonic motion from Hooke's law.

Statistical Significance Calculator

Convert between sigma, p-value and odds of random chance, one-tailed or two-tailed.

Supply and Demand Calculator

Market equilibrium price and quantity from supply and demand curves, with surpluses and shortages.

Torque Calculator

Force, lever length and angle to torque in N·m and lb·ft, with a diagram of the component that actually does the turning.

Wavelength ↔ Frequency Converter

Enter a wavelength or a frequency and get the other from c = λf, with photon energy and the spectrum band shown.