Room: 12 ft × 15 ft
Length times width gives the floor area.
Area = 180 ft² = 20 yd² = 16.72 m²
Square Feet Calculator
Get the area of a room, lot or any shape in square feet, square yards, square meters and acres.
Calculator
Enter your dimensions. The result appears here instantly.
How to Calculate Square Feet
- Pick the shape that matches your space.
- Measure each dimension. You can use feet, inches, yards, millimeters, centimeters or meters, and mix them.
- Enter the values. The calculator converts everything to feet and applies the formula.
- Read the area in square feet, plus square yards, square meters and acres.
Square Footage Formulas
All lengths are converted to feet first, so the result is in square feet.
| Shape | Formula |
|---|---|
| Square | side² |
| Rectangle | length × width |
| Circle | π × (diameter ÷ 2)² |
| Triangle | ½ × base × height |
| Rectangle Border | (L + 2b)(W + 2b) − L × W |
| Circle Border | π × ((D ÷ 2 + b)² − (D ÷ 2)²) |
| Annulus (Ring) | π ÷ 4 × (outer² − inner²) |
| Trapezoid | ½ × (base 1 + base 2) × height |
Area Unit Conversions
1 ft² = 144 in²
1 yd² = 9 ft²
1 m² ≈ 10.7639 ft² (1 ft² = 0.09290304 m²)
1 acre = 43,560 ft²
Areas use the square of the length conversion. Because 1 ft = 12 in, 1 ft² = 12 × 12 = 144 in². Likewise 1 yd = 3 ft, so 1 yd² = 3 × 3 = 9 ft².
Square Feet Examples
Mixed units: 10 ft × 120 in
120 inches is 10 feet, so the area is 10 × 10.
Area = 100 ft² = 11.11 yd² = 9.29 m²
Circle: 10 ft across
Area is π × (diameter ÷ 2)² = π × 5².
Area = 78.54 ft² = 8.73 yd² = 7.3 m²
Metric: 4 m × 3 m
Metric inputs are converted exactly (1 ft = 0.3048 m) and shown in square feet too.
Area = 129.17 ft² = 14.35 yd² = 12 m²
Adding Extra for Cuts and Waste
Flooring, tile, paint and turf are often bought with extra to allow for cuts and mistakes. The waste field is optional and starts at 0%. Enter your own percentage and the result shows the area including that allowance, and the cost if you add a price.
Square Feet Calculator FAQ
How do I calculate square feet?
For a rectangle, multiply length by width, both in feet. For other shapes, use the matching formula in the table above, or choose the shape in the calculator.
How do I convert square inches to square feet?
Divide by 144, because 1 square foot is 12 in × 12 in = 144 square inches. Do not divide by 12; that works for lengths, not areas.
How many square feet are in a square yard?
Nine. A square yard is 3 ft × 3 ft = 9 ft².
How do I measure an L-shaped or irregular room?
Split it into rectangles, find each area, and add them. For example, a 12 ft × 10 ft section (120 ft²) plus a 6 ft × 4 ft section (24 ft²) is 144 ft². The quantity field helps when you have several identical sections.
Should I add extra for flooring, paint or sod?
Cuts, patterns and trimming mean some people buy extra. The optional waste field adds the percentage you choose to the area and cost; it is 0% unless you enter a value.