Square footage is the number nearly every home project is priced on — flooring, paint, turf, tile, rent and land itself. This calculator finds the area of the four shapes that cover almost everything (rectangle, triangle, circle, trapezoid) and shows it in square feet, square metres, square yards and acres at once.
The formulas
Conversions worth knowing: 1 ft² = 0.0929 m², 1 yd² = 9 ft², and an acre is 43,560 ft² — a square about 209 ft on a side. To convert a price per m² to per ft², divide by 10.764.
Measuring awkward spaces
Break the space into the shapes above and add the results. An L-shaped room is two rectangles; a bay window area is a trapezoid or a half-circle; a triangular garden bed is one triangle. When measuring for materials, always round each dimension up to the next inch (or cm) — measuring short costs a second delivery, measuring long costs a little trim.
Worked example
A bedroom 12 ft × 10 ft: area = 120 ft². That is 11.15 m², 13.33 yd², or 0.0028 acres. At $4 per ft² for flooring, the material budget is $480 before waste — and flooring pros add 5–10% on top of the 120 ft² for cuts.
How to use this tool
- Pick the shape that matches your space and your units.
- Enter the dimensions the diagram names — for a triangle, the height is the perpendicular distance from base to tip.
- Read the area in whichever unit your supplier or listing uses.
- Optionally enter a price per square foot to turn area straight into a budget figure.
- For multi-shape spaces, run each part and add the areas together.
“Square feet” on listings vs reality
Property listings may measure area from outside walls (including wall thickness and sometimes stairs or voids), while flooring is measured inside the room. If a listing figure and your tape disagree by 5–10%, both can be “right” — they are counting different things. For buying materials, always trust your own inside measurements.