How to use the square footage calculator
Area is the number almost every design decision leans on. It sets flooring and paint quantities, furniture layouts, rent, construction budgets and whether a scheme fits its zoning. Few rooms are perfect rectangles, so this calculator lets you build a floor plan out of simple shapes and adds them up for you.
- Choose feet or metres. Enter every dimension in the same unit. Switching units converts the numbers you've already typed.
- Add a row for each room or part of a room. Pick a rectangle, an L-shape (two rectangles), a triangle or a circle, and enter the dimensions that appear.
- Add a waste allowance if you're ordering flooring, tile or carpet, so the result shows how much to buy rather than just the net area.
The results show the total in both square feet and square metres, the order quantity with waste, the number of rooms counted and the largest room. A breakdown of every room appears underneath, so you can copy it into an area schedule.
Area formulas
Rectangle = Length × Width
L-shape = (Length A × Width A) + (Length B × Width B)
Triangle = Base × Height ÷ 2
Circle = π × (Diameter ÷ 2)²
m² = ft² × 0.092903 · ft² = m² × 10.7639
Any floor plan made of straight walls can be broken into rectangles and triangles. The trick with L-shapes and more complex rooms is to split them so that the pieces don't overlap. Draw a line across the plan from one inside corner, measure each rectangle separately and add them. For a room with an angled corner, measure the full rectangle and subtract the missing triangle, or add the rectangle and triangle that make up what's left.
| Square feet | Square metres | Typical space |
|---|---|---|
| 50 ft² | 4.6 m² | Small bathroom |
| 120 ft² | 11.1 m² | Double bedroom |
| 250 ft² | 23.2 m² | Open-plan living room |
| 1,000 ft² | 92.9 m² | Two-bedroom apartment |
| 2,500 ft² | 232.3 m² | Large family house |
Worked examples
A single rectangular bedroom
The room measures 12 ft by 15 ft. Area = 12 × 15 = 180 ft², which is 16.72 m². With a 10% waste allowance for laminate, order 198 ft² of flooring.
An L-shaped living and dining room
The main space is 20 ft by 12 ft and the dining alcove is 10 ft by 8 ft. Split along the inside corner: 240 ft² + 80 ft² = 320 ft², or 29.73 m². Measuring the whole thing as one 20 × 20 ft box would overstate it by 80 ft² and send you to the store for a lot of unnecessary flooring.
A small metric apartment
The living room is 5.4 × 4.2 m (22.68 m²), the bedroom 3.6 × 3.3 m (11.88 m²) and the bathroom 2.4 × 1.8 m (4.32 m²). The total net internal area is 38.88 m², or about 418.5 ft². Add hall and storage areas as extra rows to get the full figure.
Who this calculator helps
- Architects building quick area schedules for briefs, checking room sizes against space standards and feeding gross floor area into feasibility studies.
- Interior designers working out flooring, rug and wallcovering quantities and testing whether a furniture layout leaves enough circulation space.
- Architecture students checking the areas in studio projects against the brief without opening CAD.
- Contractors and flooring installers pricing jobs per square foot or square metre and ordering materials with the right waste factor.
- Real estate agents and landlords confirming listing areas and price per square foot.
- Homeowners planning a renovation, comparing quotes or converting a listing in square metres to square feet.
Measuring tips for accurate results
- Use a laser measure where you can, and measure each wall at floor level, because walls are rarely perfectly straight or square.
- Round to the nearest inch or centimetre while measuring, not to the nearest foot. Rounding a 12'-5" wall down to 12 ft loses over 5 ft² in a 15 ft room.
- Leave out fixed items such as kitchen islands and built-in cabinets when you're ordering flooring that won't run underneath them.
- Working from drawings instead of on site? Take dimensions off a scaled plan with the architectural scale converter, then check the total against your zoning limit with the floor area ratio calculator.
Once you know the area, see what the finished floor will look like: upload a photo of the room and try oak, tile or polished concrete with AI Flooring.
