Square Footage Calculator
Area for any shape — rectangle, circle, triangle, trapezoid or several rooms at once — in ft², m², yd² and acres, with an optional cost per square foot.
Your areas
Total area
180 ft²
- Square metres
- 16.72 m²
- Square yards
- 20 yd²
How this is calculated
Area
length × width
= 12 × 15
180 ft²
How to calculate square footage
For a rectangle, multiply length by width. A 12 ft × 15 ft room is 12 × 15 = 180 ft² (16.72 m², 20 yd²). For odd-shaped spaces, break the floor into rectangles, triangles and circles, work out each area, and add them up — the multi-area mode does exactly that.
Area formulas by shape
| Shape | Formula | Example | Area |
|---|---|---|---|
| Rectangle | length × width | 12 × 15 | 180 ft² |
| Square | side² | 10² | 100 ft² |
| Circle | π × (diameter ÷ 2)² | π × 5² | 78.54 ft² |
| Triangle | 0.5 × base × height | 0.5 × 10 × 8 | 40 ft² |
| Trapezoid | 0.5 × (a + b) × height | 0.5 × (10 + 14) × 8 | 96 ft² |
Square footage conversions
| Square feet | Square metres | Square yards | Acres |
|---|---|---|---|
| 100 ft² | 9.29 m² | 11.11 yd² | 0.0023 |
| 500 ft² | 46.45 m² | 55.56 yd² | 0.0115 |
| 1,000 ft² | 92.90 m² | 111.11 yd² | 0.0230 |
| 2,500 ft² | 232.26 m² | 277.78 yd² | 0.0574 |
| 10,000 ft² | 929.03 m² | 1,111.11 yd² | 0.2296 |
| 43,560 ft² | 4,046.86 m² | 4,840 yd² | 1.0000 |
Now calculate materials for this area
Once you know the square footage, size the materials:
Common square footage mistakes
- •Mixing units. Convert everything to one unit before multiplying — the unit toggle keeps a whole project consistent.
- •Using radius vs diameter for circles. This tool takes the diameter and halves it for you.
- •Forgetting waste on materials. Square footage is exact; flooring, tile and paint need a waste factor added on top.
Frequently asked questions
How do I calculate square footage?+
Multiply length by width for a rectangular space. A 12 ft × 15 ft room is 180 square feet. For other shapes use the matching formula: circle = π × radius², triangle = 0.5 × base × height, trapezoid = 0.5 × (a + b) × height.
How many square feet are in a square metre?+
One square metre is 10.7639 square feet. To convert square feet to square metres, multiply by 0.09290304 (the exact factor). So 180 ft² = 16.72 m².
How do I calculate the square footage of an irregular room?+
Split the room into simple shapes — rectangles, triangles and circles — calculate each area, then add them together. Use the “add another area” button to sum several shapes at once.
How many square feet are in an acre?+
One acre is exactly 43,560 square feet (4,046.86 m²). The calculator shows acres automatically once the total area is large enough.
Methodology & sources
Area is computed with the standard geometric formulas for each shape, carrying full precision and using exact π. Multi-area mode sums each shape’s area. Unit conversions use the exact factors 1 ft² = 0.09290304 m², 1 yd² = 9 ft² and 1 acre = 43,560 ft².
Square footage is exact — when ordering flooring, tile or paint, add a waste factor with the matching material calculator before you buy.
Last reviewed June 28, 2026. Estimates are indicative — verify against current product specs and local requirements before ordering.
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