Square Footage Calculator
What Is a Square Footage Calculator?
A square footage calculator computes the area of a room, floor, yard, or any flat surface in square feet. Square footage is the standard unit for measuring interior space in the United States — used by real estate agents quoting home sizes, flooring contractors pricing jobs, painters estimating paint cans, and landlords calculating rent per square foot.
The basic formula for a rectangular room is Area = Length × Width. A 12-foot by 15-foot bedroom has 180 square feet. For non-rectangular spaces — circles, triangles, L-shapes — you calculate each sub-area separately and add them together.
This calculator supports rectangles, circles, triangles, and trapezoids, converts automatically to square yards and square meters, and optionally multiplies by a price per square foot to estimate flooring, tile, carpet, or paint costs.
How to Use This Square Footage Calculator
- Select the shape of your room or area (rectangle, circle, triangle, or trapezoid).
- Enter measurements in feet. Use decimal feet for inches — 6 inches = 0.5 ft, 9 inches = 0.75 ft.
- Optionally enter a price per square foot for flooring, tile, or carpet to get a material cost estimate.
- Click Calculate Square Footage to see area in ft², yd², and m².
- For L-shaped or irregular rooms, calculate each rectangle separately and add the results.
Worked Example: Flooring a 3-Room Apartment
Jordan is installing hardwood floors at $4.50/ft² in three rooms:
| Room | Dimensions | Square Feet | Cost @ $4.50/ft² |
|---|---|---|---|
| Living Room | 18 × 22 ft | 396 ft² | $1,782 |
| Bedroom | 12 × 14 ft | 168 ft² | $756 |
| Hallway | 4 × 20 ft | 80 ft² | $360 |
| Total | 644 ft² | $2,898 |
Always add 10% waste for cuts and mistakes: 644 × 1.10 = 708 ft² to purchase.
Square Footage Reference Table
| Space | Typical Size (ft²) | Notes |
|---|---|---|
| Studio apartment | 400–600 | Open floor plan |
| 1-bed apartment | 600–900 | Separate bedroom |
| 2-bed apartment | 900–1,200 | US average |
| Single-family home | 1,600–2,400 | US median ~2,014 ft² |
| Master bedroom | 200–300 | Typical range |
| Standard bedroom | 120–180 | 10×12 to 12×15 |
| Parking space | 160–200 | 8.5×18 to 9×20 |
Area Formulas for Every Shape
- Rectangle / Square: Area = Length × Width
- Circle: Area = π × Radius² (π ≈ 3.14159)
- Triangle: Area = ½ × Base × Height
- Trapezoid: Area = ½ × (Base1 + Base2) × Height
- L-shaped room: Split into two rectangles, calculate each, add together
- Unit conversions: 1 ft² = 0.111 yd² = 0.0929 m²
For irregular shapes, photograph and divide into known shapes. Measure each sub-area carefully — a 3-inch error in one dimension of a 20-foot room adds or removes 5 square feet.
Tips and Common Mistakes
- Convert inches to decimal feet first: 8 inches = 0.667 ft. Measure in decimals to avoid rounding errors.
- Add 10% overage for flooring: Tile, hardwood, and laminate all require extra for cuts and waste. Some patterns need 15%.
- Paint covers 350 ft² per gallon: Calculate wall square footage (perimeter × height), subtract doors and windows, divide by 350.
- Carpet is sold by the yard: Divide ft² by 9 to get yd² for carpet ordering.
- Real estate sq ft excludes unfinished spaces: Finished basement and garage often excluded from listed square footage.
Frequently Asked Questions About Square Footage
How do I calculate square footage of an L-shaped room?
Divide the L-shape into two rectangles. Measure each separately and add the areas. For example, a 20×10 rectangle plus a 10×8 rectangle = 200 + 80 = 280 ft².
How many square feet is a 10×10 room?
A 10×10 room is exactly 100 square feet. This is a common kitchen or small bedroom size.
How do I convert square feet to square meters?
Multiply square feet by 0.0929. A 1,500 ft² house = 1,500 × 0.0929 = 139.4 m².
How much flooring do I need for 500 square feet?
Buy 10% extra for waste: 500 × 1.10 = 550 ft² of material. For tile with a pattern, add 15% instead.
What is the square footage of a 12×12 room?
12 × 12 = 144 square feet. A standard bedroom size in most US homes.
How do I measure square footage of a house?
Measure the exterior footprint (length × width of each floor), subtract garage and unfinished areas. Walk the perimeter with a measuring tape or laser measure, room by room.
How many square feet in an acre?
One acre = 43,560 square feet. A football field is about 48,000 ft² including end zones.
How do I calculate square footage for a circular room?
Use Area = π × r². For a round room with a 12-foot radius: 3.14159 × 144 = 452 ft². Enter the radius into the circle option above.