Square Footage Calculator
Get the square footage of any rectangular, triangular or circular area — with instant conversions.
Enter your measurements to see what to buy.
How to calculate it
Get the square footage of any rectangular, triangular or circular area — with instant conversions.
Source: Standard area formulas. 1 square yard = 9 ft²; 1 square meter ≈ 10.764 ft²; 1 acre = 43,560 ft².
A 15×20 ft living room = 300 ft² = 33.33 yd² = 27.87 m². An L-shaped room: split into two rectangles and add the results.
Want the full step-by-step walkthrough? Read our How to Plan and Pour a Concrete Patio Slab.
Square footage conversions
Square footage is the starting number for almost every material estimate. This table lists the conversions you will use most often when comparing products and prices.
| Unit | Equals in square feet | Common use |
|---|---|---|
| 1 square yard | 9 ft² | Carpet pricing |
| 1 square meter | 10.764 ft² | Metric conversion |
| 1 acre | 43,560 ft² | Large lots, land |
| 1 cubic yard | 27 ft³ (volume) | Concrete, mulch, gravel |
For L-shaped or irregular rooms, split the area into simple rectangles or triangles, calculate each, and add the results.
How to use this calculator
- Pick a shape — rectangle, triangle or circle — and enter its dimensions in feet and inches.
- The calculator returns square feet plus conversions to square yards, square meters and acres.
- For L-shaped or irregular areas, split into rectangles and add the results.
- Use the result as the starting input for flooring, paint, tile and sod calculators.
Purchasing & waste guidance
- 1 square yard = 9 square feet.
- 1 square meter ≈ 10.764 square feet.
- 1 acre = 43,560 square feet.
- For L-shaped rooms, split into two rectangles and add the results.
Waste factor guidance
- No waste is added — this tool measures area only, not material.
- Apply waste in the material calculator that uses this square footage.
- For irregular shapes, measure each section separately and add them for an accurate total.
Common mistakes to avoid
- Measuring in inches and forgetting to convert — enter feet and inches in the paired boxes.
- Including non-floor area like wall thickness when calculating for flooring or paint.
- Using the exterior footprint instead of interior dimensions for interior material estimates.
Assumptions & what’s included
- Measurements are entered in feet and inches.
- Conversions use standard factors (yd², m², acres).
- For irregular shapes, break the area into simple rectangles or triangles and add them.
Sources & references
- Unit conversions use standard factors: 1 square yard = 9 ft², 1 square meter ≈ 10.764 ft², 1 acre = 43,560 ft² (NIST / U.S. survey foot convention).
- Area formulas (rectangle L×W, triangle ½bh, circle πr²) are standard geometric formulas.
- 1 cubic yard = 27 cubic feet is the standard volume conversion used for concrete, mulch and gravel estimates.
Learn more about how every calculator works on our methodology page.
Frequently asked questions
How do I calculate square footage?
For a rectangle, multiply length × width in feet. For a triangle, (base × height) ÷ 2. For a circle, π × (diameter ÷ 2)². The calculator does all three and converts units.
How many square feet is a 12×12 room?
A 12×12 ft room is 144 square feet, or 16 square yards. That’s the starting number for flooring, paint and tile estimates.
How do I measure square footage of an L-shaped room?
Split the room into two rectangles, calculate each one’s area, and add them together. The same approach works for any irregular shape.
How many square feet are in an acre?
One acre equals 43,560 square feet. The calculator converts your result to acres automatically, which is useful for large lots and lawn estimates.
How many square feet is a 10×10 room?
A 10×10 ft room is 100 square feet, or about 11.1 square yards. That is the starting number for flooring, paint and tile estimates for the room.
How do I calculate square footage for flooring?
Multiply the room length × width in feet to get square footage, then add a waste allowance (10% for straight-lay flooring) before dividing by the coverage per box. Use the Flooring Calculator once you have the square footage.
Related guides
Step-by-step project guides that use this calculator.