Square footage calculator
Enter each room as a rectangle, an L-shape, a circle or a triangle, in feet and inches or in metres. The calculator gives every room's area and the total in square feet and square metres, sketches the rooms to scale and shows each one's share of the total.
Square footage calculator
- 272 ft²ftinftinftinftin
The overall rectangle, less the rectangle missing from one corner (drawn at the top right).
- 99 ft²ftinftin
- 156 ft²ftinftin
- 110 ft²ftinftin
- 40 ft²ftinftin
Measure inside the walls for floor area; listings usually quote the outside. Open as a floor plan builds the rectangles and L-shapes (each L as one room, its cut-out at the top right); circles and triangles stay here.
Total floor area
677 ft²
- Square feet
- 677
- Square metres
- 62.9
- Rooms
- 5
- Largest room
- Living and dining
Sketch, to scale
Share of the total
- Living and dining272 ft²40%
- Kitchen99 ft²15%
- Bedroom 1156 ft²23%
- Bedroom 2110 ft²16%
- Bathroom40 ft²6%
The formula
The area of a rectangular room is its length × width. Work in one unit: turn inches into decimal feet first (6 in is 0.5 ft, 9 in is 0.75 ft), multiply, then add the rooms together. To get square metres, multiply square feet by 0.09290304 (or use the ft² to m² converter).
- Measure each room wall to wall at floor level, in two directions.
- Convert inches to feet: divide by 12.
- Work out each room's area by its shape (below).
- Add the rooms.
| Shape | Measure | Area | Example |
|---|---|---|---|
| Rectangle | Length and width | length × width | 14 × 12 ft = 168 ft² |
| L-shape | The overall length and width, and the rectangle missing from one corner | length × width − cut-out length × cut-out width | 20 × 16 ft less 8 × 6 ft = 272 ft² |
| Circle | The diameter, wall to wall through the centre | π × diameter² ÷ 4 | 10 ft across = 78.5 ft² |
| Triangle | The base, and the height square to it | base × height ÷ 2 | 8 ft base, 6 ft high = 24 ft² |
An L can also be split into two rectangles that do not overlap: the 20 × 16 ft L above is a 20 × 10 ft part (200 ft²) and a 12 × 6 ft part (72 ft²), 272 ft² either way. Open as a floor plan builds the L as one room, with the cut-out at the top right as the sketch draws it; circles and triangles stay in the calculator. A half-round bay is half a circle: work out the full circle and halve it.
Worked examples
A two-bedroom apartment. The calculator opens on one: an L-shaped living and dining room (20 × 16 ft less 8 × 6 ft, 272 ft²), an 11 × 9 ft kitchen (99 ft²), bedrooms of 13 × 12 and 11 × 10 ft (156 and 110 ft²) and an 8 × 5 ft bathroom (40 ft²): 677 ft², or 62.9 m². The living and dining room is 40% of it.
Feet and inches. A bedroom 11 ft 6 in × 13 ft 9 in is 11.5 × 13.75 = 158.1 ft², or 14.69 m².
Several rooms. FloorGen's 3-bed ranch template has a living room of 16 × 20 ft, a 12 × 12 ft bedroom and a 14 × 12 ft bedroom on its wall grid. That is 320 + 144 + 168 = 632 ft² (58.7 m²).
Now the catch. Those grid sizes run along the wall centrelines. Measured to the inside faces of the walls, which is what you get with a tape measure, the same three rooms are 305.3, 134.1 and 156.3 ft²: 595.7 ft², about 6% less. Both numbers are right; they measure different things. Measure inside the walls for flooring and paint; listings and appraisals measure the outside of the house.
| Room size | Square feet | Square metres | Typical use |
|---|---|---|---|
| 10 × 10 ft | 100 ft² | 9.29 m² | Small bedroom or home office |
| 10 × 12 ft | 120 ft² | 11.15 m² | Secondary bedroom |
| 12 × 12 ft | 144 ft² | 13.38 m² | Bedroom with a queen bed |
| 12 × 15 ft | 180 ft² | 16.72 m² | Kitchen or small living room |
| 14 × 16 ft | 224 ft² | 20.81 m² | Primary bedroom |
| 16 × 20 ft | 320 ft² | 29.73 m² | Living room |
| 20 × 20 ft | 400 ft² | 37.16 m² | Two-car garage (minimum workable) |
Which square footage do you need?
| Measure | Measured to | Used for |
|---|---|---|
| Net room area | The inside faces of the walls | Flooring, paint, furniture layout; what FloorGen labels each room with |
| Gross area | Wall centrelines or the outside of the walls | Builders' plans, construction cost per square foot |
| ANSI Z765 finished area | The outside of the house, finished space only | Appraisals and listings; garages and below-grade space are reported apart |
The rules for the last one, including ceiling heights and stairs, are in how to calculate square footage (ANSI Z765). To measure a room well in the first place, see how to measure a room for a floor plan.
Let a floor plan do the adding
If the rooms are not rectangles, or you want the total to stay right while you move walls, draw them. In FloorGen every closed room is labeled with its net area as you draw, and the Plan summary (the area chip at the top left of the plan) lists the rooms with a total and exports them as CSV.
Questions
How many square feet is a 12 × 12 room?
144 ft², which is 13.38 m². A 10 × 12 ft room is 120 ft² and a 12 × 14 ft room 168 ft².
How do I find the square footage of an L-shaped room?
Take the overall length × width, then subtract the rectangle missing from the corner: a 20 × 16 ft L with an 8 × 6 ft notch is 320 − 48 = 272 ft². Or split it into two rectangles that do not overlap and add them. In the calculator, pick L-shape for the room.
How do I measure a round or triangular room?
For a circle, measure the diameter through the centre: the area is π × diameter² ÷ 4, so 10 ft across is 78.5 ft². For a triangle, measure one side as the base and the distance square to it to the far corner as the height: the area is base × height ÷ 2.
Does square footage include the walls?
It depends on who is measuring. Room areas for flooring are measured inside the walls. Appraisers and listings measure the outside of the house, so walls are included and the figure is larger, often by around 10%: FloorGen's 800 sq ft ADU template has 700.5 ft² of rooms inside its walls.
Do closets and hallways count?
In a whole-house figure, yes: closets, halls and stairs are finished space. Garages, unfinished attics, porches and decks do not count toward finished area under ANSI Z765.
How do I convert square feet to square metres?
Multiply by 0.09290304. 1,000 ft² is 92.9 m². Going the other way, multiply square metres by 10.7639.