Square Footage Calculator
Multiply length × width to find square feet for any rectangular area.
Square Footage: —
Formula
Length × Width = Square feet. Enter both measurements in feet. Decimals like 12.5 are fine.
| Length | Width | Square feet |
|---|---|---|
| 10 ft | 10 ft | 100 sq ft |
| 12 ft | 10 ft | 120 sq ft |
| 15 ft | 20 ft | 300 sq ft |
Related tools
Square Footage FAQ
What units should I enter?
Feet. If you have inches, divide by 12 first or use the feet-to-inches converter.
Can I use it for concrete slabs?
Yes — for volume, also use the Concrete Bag Calculator.
Do decimals work?
Yes — 12.5 ft by 8.75 ft works fine.
Results are estimates for planning purposes. Verify with product labels and local requirements before purchasing materials.
How to calculate square footage
Square footage is the area of any flat rectangular surface, measured in square feet. To find it, multiply the length by the width — both in feet.
The formula is: Square feet = Length (ft) × Width (ft)
If your measurements are in inches, divide each one by 12 before multiplying. If you have a room with an unusual shape, break it into smaller rectangles, calculate each section separately, then add the totals together.
Square footage formula with worked examples
| Space | Length | Width | Square feet |
|---|---|---|---|
| Bedroom | 12 ft | 12 ft | 144 sq ft |
| Living room | 15 ft | 20 ft | 300 sq ft |
| Patio | 10 ft | 14 ft | 140 sq ft |
| 2-car garage | 20 ft | 22 ft | 440 sq ft |
| Concrete slab | 8 ft | 10 ft | 80 sq ft |
| Driveway | 10 ft | 30 ft | 300 sq ft |
Common uses for square footage calculations
Knowing the square footage of a surface is the starting point for almost every home improvement and construction estimate.
Flooring and carpet
Tile, hardwood, laminate, vinyl plank, and carpet are all sold by the square foot or square yard. Always add 10–15% to your calculated area for waste and cuts.
Paint coverage
A gallon of paint typically covers 350–400 square feet per coat. Calculate your wall area — perimeter of the room × ceiling height — and subtract doors and windows to estimate gallons needed.
Concrete and paving
Slabs, driveways, patios, and sidewalks are priced and planned by square footage. Use the area to calculate concrete volume and bag counts.
Landscaping materials
Sod, mulch, gravel, and topsoil are all estimated using square footage. Most bulk materials are then converted to cubic yards based on the desired depth.
How to measure irregular and L-shaped spaces
Many rooms and outdoor spaces are not simple rectangles. The standard approach is to divide the space into two or more rectangles, calculate each, and add them together.
Example: L-shaped living room
Section A: 15 ft × 12 ft = 180 sq ft
Section B: 8 ft × 10 ft = 80 sq ft
Total: 180 + 80 = 260 square feet
For triangular areas, use: ½ × base × height. For circular areas: π × radius² (approximately 3.14159 × radius in feet × radius in feet).
Frequently asked questions about square footage
How do I calculate square footage?
Multiply the length in feet by the width in feet. For example, a room 12 feet long and 10 feet wide is 120 square feet. For irregular spaces, break them into rectangles, calculate each separately, then add the totals.
How many square feet is a 12x12 room?
A 12×12 foot room is exactly 144 square feet. This is a common bedroom size and a useful reference point for estimating flooring or paint needs.
How do I convert square feet to square yards?
Divide square feet by 9 to get square yards. For example, 270 square feet equals 30 square yards. This matters for carpet, which is typically sold by the square yard.
How many square feet in an acre?
One acre equals 43,560 square feet. To convert your square footage to acres, divide by 43,560.
How much extra flooring should I order?
Order 10% extra for straight-lay patterns. Order 15% extra for diagonal tile or herringbone patterns due to additional cuts. Always buy from the same production batch to ensure color consistency.
How do I calculate square footage for an L-shaped room?
Divide the L-shape into two separate rectangles. Measure each section independently, calculate each area, then add the two totals together for the complete square footage.
What is the formula for square footage?
Square footage = Length (ft) × Width (ft). Both measurements must be in the same unit — feet. If you have inches, divide by 12 to convert to feet first.
How do I measure a room accurately for flooring?
Measure from wall to wall at floor level, not at baseboard height. Take two measurements per dimension in case walls are not perfectly straight. Use the larger measurement to avoid coming up short on materials.
Related tools
- Concrete Bag Calculator — estimate bags needed for your slab area
- Paint Coverage Calculator — find out how much paint you need
- Tile Calculator — estimate tile quantity from your area
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