Square Footage Calculator
Area of a room, a lot or an odd shape from rectangles, triangles and circles added together, in square feet, yards, metres and acres with exact factors.
Area of a room, a lot or an odd shape, from rectangles, triangles and circles added together, in square feet, yards, metres and acres — with the exact factors between them.
Up to four shapes, added together. Leave a shape’s dimensions blank to skip it; use the negative quantity to subtract a cut-out.
| 1 | — |
|---|---|
| 2 | — |
| 3 | — |
| 4 | — |
| Square feet | — |
| Square yards | — |
| Square metres | — |
| Acres | — |
Any floor plan is rectangles, triangles and circles. An L-shaped room is two rectangles; a bay window is a rectangle and two triangles; a round patio is a circle. Measure each piece, add them, and subtract the pieces that are not floor — a stair opening, an island — with a negative quantity. Four shapes cover most rooms; a plan that needs more is worth drawing rather than adding.
The factors are exact, not rounded. A square foot is 0.09290304 m² by definition, a square yard is 9 ft², an acre is 43,560 ft². Rounded factors like 0.093 are fine for a room and wrong by a bathroom on an acre; the page uses the definitions and rounds only what it prints.
Measured to what? Flooring wants the finished floor, wall to wall. A lease wants the rentable area, which includes things you cannot stand on. A lot wants the survey. The number is only as good as the question it answers, and this page answers the one you measured.
Rectangle = length × width; triangle = ½ base × height; circle = π (d ÷ 2)². Totals use 1 ft² = 0.09290304 m² (exact), 1 yd² = 9 ft², 1 acre = 43,560 ft².
Worked example
A 15 × 12 ft room with a triangular bay 10 ft wide and 8 ft deep, and a round 10 ft patio: total square footage?
- Rectangle 15 × 12 = 180 ft²; triangle ½ × 10 × 8 = 40 ft²; circle π × 5² = 78.54 ft².
- Total 298.54 ft².
- ÷ 9 = 33.17 yd²; × 0.09290304 = 27.74 m²; ÷ 43,560 = 0.00685 acre.
298.5 square feet, or 33.2 square yards. A cut-out — a stair opening, an island — goes in as a shape with quantity −1.
7 values on this page were driven in a browser and compared with independently derived figures on 2026-09-05 (418 values across 51 calculators site-wide).
Questions
How do you calculate square footage of an L-shaped room?
As two rectangles added together: measure each leg's length and width, multiply, and sum. A cut-out is a rectangle subtracted.
How many square feet in a square yard and an acre?
9 and 43,560. A square metre is 10.7639 ft² (1 ft² = 0.09290304 m² exactly).