Square Footage Calculator
Work out the square footage of rooms and floors of any common shape in feet and inches or meters, add several areas together, and estimate material cost with a waste allowance.
Square Footage Calculator
Example Enter your own measurements above.
291.5 sq ft
Total of 2 areas · 27.08 m²
Add a price below to estimate the cost.
Working
- Area 1 (Living room): 12 ft 6 in = 12.5 ft, so 15 ft × 12.5 ft = 187.5 sq ft (17.42 m²)
- Area 2 (Kitchen): 10 ft × 8 ft + 6 ft × 4 ft = 80 + 24 = 104 sq ft (9.66 m²)
- Total = 187.5 + 104 = 291.5 sq ft
- Square yards = 291.5 ÷ 9 = 32.3889
- Square meters = 291.5 × 0.09290304 = 27.0812
- Acres = 291.5 ÷ 43,560 = 0.006692
How to use the square footage calculator
Choose whether you measured in feet and inches or in meters. For each room or section, pick its shape and type the measurements — the small diagram shows which side is which, and the line under each area shows the formula with your numbers. Press Add another area for the next room, closet or hallway; the total underneath adds every area and converts it to square feet, square yards, square meters and acres. Two example areas are filled in to start with.
For a material estimate, enter a price per square foot, square yard or square meter and, if you want, a waste allowance. Switching between feet and meters converts what you have already typed, so the areas stay the same. The page address keeps your shapes, measurements and price so you can bookmark or share them; area names stay on your device. Nothing is sent anywhere — the calculations run in your browser.
Area formulas
| Shape | Formula | Example |
|---|---|---|
| Rectangle or square | L × W | 15 ft × 12.5 ft = 187.5 sq ft |
| L-shape | L₁ × W₁ + L₂ × W₂ | 10 × 8 + 6 × 4 = 104 sq ft |
| Circle | π × (D ÷ 2)² | D = 8 ft: π × 4² ≈ 50.27 sq ft |
| Triangle | ½ × b × h | ½ × 10 ft × 6 ft = 30 sq ft |
| Triangle, three sides | √(s(s − a)(s − b)(s − c)), s = (a + b + c) ÷ 2 | 3, 4, 5 ft: s = 6, √(6 × 3 × 2 × 1) = 6 sq ft |
| Trapezoid | (a + b) ÷ 2 × h | (6 ft + 10 ft) ÷ 2 × 4 ft = 32 sq ft |
The height of a triangle or trapezoid is measured at a right angle to the base, not along a sloping side. If that is hard to measure, use Triangle (three sides), which needs only the three side lengths (Heron’s formula). The unit conversions are exact because the foot is defined as exactly 0.3048 m:
1 ft = 12 in = 0.3048 m
1 sq ft = 144 sq in = 0.09290304 m²
1 sq yd = 3 ft × 3 ft = 9 sq ft
1 acre = 43,560 sq ft ≈ 4,046.86 m²
1 m² ≈ 10.7639 sq ft Worked example
These are the two example areas already in the calculator:
- Living room, 15 ft × 12 ft 6 in. Six inches is 6 ÷ 12 = 0.5 ft, so the width is 12.5 ft and the area is 15 × 12.5 = 187.5 sq ft.
- L-shaped kitchen. Split into a 10 ft × 8 ft part (80 sq ft) and a 6 ft × 4 ft part (24 sq ft): 104 sq ft.
- Total: 187.5 + 104 = 291.5 sq ft, which is 291.5 ÷ 9 = 32.39 sq yd, 291.5 × 0.09290304 = 27.08 m², or 291.5 ÷ 43,560 = 0.006692 acres.
Now enter a price of $4.00 per sq ft (an illustration, not a typical price) and a 10% waste allowance. The calculator shows 291.5 × 1.1 = 320.65 sq ft of material to buy, costing 320.65 × $4.00 = $1,282.60, compared with $1,166.00 for the exact floor area.
How to measure a room
- Measure wall to wall at floor level, along the longest straight lines, and round up to the next inch. A laser measure makes long rooms easier.
- Split irregular rooms into rectangles and triangles that do not overlap, and add closets, alcoves and hallways as separate areas.
- Inches are not decimals. 12 ft 6 in is 12.5 ft, not 12.6 ft. Type feet and inches in their own boxes and the calculator converts them.
- “Square feet” is not “feet square”. 10 square feet is any area of that size (such as 2 ft × 5 ft); a room 10 feet square is 10 ft × 10 ft = 100 sq ft.
- Check the units of the price. Carpet is often priced per square yard and hard flooring per square foot. A price per square yard is 9 times the equivalent price per square foot.
Waste allowance
You rarely buy exactly the floor area. Pieces are cut to fit walls and doorways, patterns have to line up, and some pieces break. Flooring estimates commonly add about 5–10%, but the right figure varies with the material, the room’s shape and the layout, so use the amount your supplier or installer recommends. Flooring sold by the box or roll also needs rounding up to whole units: divide the area to buy by the coverage printed on the box. Keeping a few spare pieces from the same batch makes later repairs easier to match.
Square footage of a whole home
Adding rooms measured from the inside is ideal for flooring and paint, but it will not match a listing or appraisal exactly: it leaves out wall thickness and any space you skipped. For appraisals on most mortgages sold to Fannie Mae, appraisers must measure and report square footage using the ANSI Z765-2021 standard, which reports above-grade and below-grade finished area separately. If square footage affects a price, ask how it was measured. The mortgage calculator can help once you know what a home costs.
Converting area units
For quick conversions and tables, use the square feet to square meters, square meters to square feet, square meters to square yards, square feet to acres and acres to hectares converters, or browse all area converters. For single lengths, see feet to meters and inches to feet.
Frequently asked questions
How do I calculate square footage?
Measure the length and width in feet and multiply them. A room 12 ft by 15 ft is 12 × 15 = 180 sq ft. For a room that is not a rectangle, split it into rectangles, triangles or other simple shapes, work out each one and add them together.
How do I calculate square footage with feet and inches?
Turn the inches into a fraction of a foot by dividing by 12, then multiply. 12 ft 6 in is 12 + 6 ÷ 12 = 12.5 ft, so 15 ft × 12 ft 6 in = 15 × 12.5 = 187.5 sq ft. Alternatively, multiply the measurements in inches and divide by 144 (the square inches in a square foot).
How many square feet are in a square yard, a square meter and an acre?
A square yard is 3 ft × 3 ft = 9 sq ft. A square meter is about 10.764 sq ft (exactly 1 ÷ 0.09290304). An acre is 43,560 sq ft. See the square meters to square feet and acres to square feet converters for tables.
How do I find the square footage of an L-shaped room?
Split the L into two rectangles that do not overlap, calculate each one and add them. A 10 ft × 8 ft section plus a 6 ft × 4 ft section is 80 + 24 = 104 sq ft. Choose the L-shape option and the calculator does the split sum for you.
How much extra flooring should I buy?
Estimates commonly add about 5–10% for cuts, offcuts and mistakes, but the right amount varies with the material, the room’s shape and the layout pattern — follow your supplier’s or installer’s advice. Round up to whole boxes or rolls, and consider keeping a few spare pieces for future repairs.