Tools & Data
Math, unit conversions, dates and time — the core tools and data calculators.
Math31
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.