How do you calculate a room's size?
For a rectangular room, length × width gives the floor area. A 4 m × 3 m room is 12 m² (about 129 sq ft). For an L-shaped room, split it into two rectangles, work out each, and add them. Ceiling height doesn't change floor area but matters for how big the room feels — and for paint and heating, where you'd use the wall area or the volume instead. The calculator above gives the floor area in both metric and imperial as you type.
What is an average room size?
It varies by country and home, but as a guide: a main bedroom is often around 12–20 m² (130–215 sq ft), a second bedroom 9–12 m², a living room 15–30 m², and a kitchen 8–15 m². A single bedroom under about 7 m² starts to feel tight, while anything over ~25 m² reads as generous. The calculator shows where your room lands on that scale so you can tell at a glance if it's small, average or large.
Will my furniture fit?
Area alone doesn't tell you if a layout works — proportions and clearances do. As rules of thumb: leave 60–75 cm (24–30 in) of walkway around a bed and between furniture, allow a 2.4–3 m wall for a standard sofa, and keep 1 m in front of wardrobes and drawers to open them. Knowing the exact dimensions (not just the area) lets you check a bed, sofa or table against the wall lengths before you buy or move it.
Square metres, square feet and 'squares'
The same floor can be described several ways, which trips people up. 1 square metre = 10.76 square feet, so a 20 m² room is about 215 sq ft. In some countries (Australia, parts of the US building trade) floor area is quoted in 'squares', where one square = 100 sq ft ≈ 9.29 m². The calculator shows metric and imperial side by side so a listing, a floor plan and a furniture spec all line up.
Average sizes are general guides and vary by country, era and home. Measure your own walls for anything you plan to build or furnish.
Frequently asked questions
How do I calculate the size of a room?
Multiply length by width for a rectangular room: a 4 × 3 m room is 12 m² (129 sq ft). For an L-shape, split it into rectangles and add them.
What is a normal bedroom size?
A main bedroom is typically 12–20 m² (130–215 sq ft); a smaller second bedroom is around 9–12 m². Under ~7 m² feels tight for a bedroom.
What is the average living room size?
Roughly 15–30 m² (160–320 sq ft), depending on the home. Open-plan living-dining spaces are often larger.
How many square feet is a square metre?
1 m² = 10.76 sq ft. So 10 m² ≈ 108 sq ft and 20 m² ≈ 215 sq ft.
How much space do I need around furniture?
Leave about 60–75 cm (24–30 in) as walkways around beds and between pieces, and roughly 1 m in front of wardrobes and drawers to open them.