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How to Calculate Square Footage
Square footage is the measurement of area in square feet. It's essential for flooring, painting, landscaping, and real estate projects.
Rectangle or Square
Multiply length by width:
Example: A room 12 ft Γ 10 ft = 120 square feet
Triangle
Multiply base by height, then divide by 2:
Circle
Multiply Ο (3.14159) by the radius squared:
Complex Rooms
For L-shaped or irregular rooms, divide into rectangles, calculate each, and add them together.
On this page
Common Uses for Square Footage
Flooring
Calculate sq ft to determine how much hardwood, laminate, tile, or carpet you need. Add 10% for waste.
Paint Coverage
One gallon of paint typically covers 350-400 sq ft. Calculate wall area (height Γ perimeter) minus windows and doors.
Mulch & Landscaping
Calculate the area of garden beds to determine cubic yards of mulch needed.
Real Estate
Square footage determines home value. Measure each room and add together for total living space.
Square Footage Conversion Table
Materials are sold in whatever unit their industry uses β carpet by the square yard, tile by the square meter, land by the acre. These are the conversions you'll actually need:
| To Convert | Multiply By | Or Divide By | Example |
|---|---|---|---|
| Sq ft β sq yards | 0.1111 | 9 | 180 sq ft = 20 sq yd |
| Sq ft β sq meters | 0.0929 | 10.764 | 500 sq ft = 46.5 mΒ² |
| Sq ft β acres | 0.0000230 | 43,560 | 43,560 sq ft = 1 acre |
| Sq ft β squares (roofing) | 0.01 | 100 | 2,400 sq ft = 24 squares |
| Sq yards β sq ft | 9 | 0.1111 | 20 sq yd = 180 sq ft |
| Sq meters β sq ft | 10.764 | 0.0929 | 50 mΒ² = 538 sq ft |
| Acres β sq ft | 43,560 | β | 0.25 acre = 10,890 sq ft |
The one that trips people up is square yards. A square yard is 3 ft Γ 3 ft, so it's nine square feet, not three. Carpet quoted at "$30 a yard" is $3.33 per square foot β a much less alarming number.
Room Size Reference
Useful for sanity-checking a measurement before you order anything:
| Room | Typical Size | Square Feet | Sq Yards |
|---|---|---|---|
| Small bathroom | 5 Γ 8 ft | 40 sq ft | 4.4 |
| Bedroom | 10 Γ 12 ft | 120 sq ft | 13.3 |
| Primary bedroom | 14 Γ 16 ft | 224 sq ft | 24.9 |
| Living room | 16 Γ 20 ft | 320 sq ft | 35.6 |
| Two-car garage | 20 Γ 20 ft | 400 sq ft | 44.4 |
How to Measure a Room Accurately
Most bad material estimates come from bad measurements, not bad math. A few minutes of care here saves a return trip to the store.
- Measure at floor level, wall to wall. Baseboards, bay windows, and out-of-plumb walls all mean the measurement at waist height differs from the one at the floor.
- Measure each wall, not just two. Rooms are rarely perfectly rectangular. If opposite walls differ, use the longer figure for material and note the difference.
- Check the diagonals. In a true rectangle both diagonals are equal. If they aren't, the room is out of square β matters a great deal for tile and plank flooring layout.
- Break complex rooms into rectangles. Sketch the floor plan, split it into rectangles at every corner, and calculate each separately. Add them together.
- Include closets and alcoves if they'll be floored or painted. Exclude them if they won't.
- Record in feet and inches, then convert once. Converting each measurement as you go compounds rounding errors. Do it at the end.
- Deduct openings only where it matters. For paint, subtract windows and doors. For flooring, subtract permanent fixtures like an island or a hearth β but not doorways, where flooring usually continues.
That decimal conversion is where hand calculations most often go wrong. 8 ft 7 in is 8.58 ft, not 8.7 ft β a 1.4% error that compounds through every downstream material estimate.
Measuring Odd Shapes
- L-shaped rooms: Split into two rectangles at the inside corner. Add the areas.
- Circular areas: Measure straight across the widest point for the diameter, then halve it for the radius. Measuring a radius directly means finding the exact center, which is harder than it sounds.
- Triangles and angled bays: Base Γ height Γ· 2, where height is the perpendicular distance to the base β not the length of a sloping side.
- Curved or truly irregular beds: Overlay a grid of rectangles, count the full ones, and estimate the partials. Close enough for mulch and sod.
How Much Waste Should You Add?
Nearly every material needs an overage on top of your measured area, because of cuts, breakage, and pattern alignment. The right percentage depends on the material and the layout:
| Material | Standard Layout | Diagonal / Complex | Why |
|---|---|---|---|
| Tile | 10% | 15β20% | Perimeter cuts and breakage |
| Hardwood / laminate | 10% | 15% | End cuts and board defects |
| Carpet | 10% | 20% | Roll width forces seam placement |
| Paint | 10% | 10% | Touch-ups and second coats |
| Sod | 5β10% | 10β15% | Trimming to curved beds |
| Concrete | 10% | 10% | Uneven subgrade |
Buy the overage in the same batch for anything with color: tile, flooring, paint, and shingles all vary between production runs. A box of tile bought three weeks later can be visibly different, and there's no fixing that once it's on the floor.
Once you have your area, take it to the calculator you actually need β tile, paint, mulch, sod, or concrete.
Frequently Asked Questions
How do I convert square feet to square yards?
Divide square feet by 9. There are 9 square feet in one square yard.
How do I convert square feet to square meters?
Multiply square feet by 0.0929. Or divide by 10.764.
How much extra flooring should I buy?
Add 10% for standard installations, 15% for diagonal patterns or complex rooms.
How do I calculate square footage of a room?
Multiply the room's length by its width in feet. A 12 Γ 10 ft room is 120 square feet. For an L-shaped room, split it into two rectangles at the inside corner, calculate each, and add them together.
How many square feet are in a square yard?
Nine. A square yard is 3 ft Γ 3 ft, so it's 9 square feet β not 3. This is the most common conversion error. Carpet priced at $30 per square yard is $3.33 per square foot.
How many square feet are in an acre?
43,560 square feet. A quarter-acre lot is 10,890 sq ft, and a half-acre is 21,780. For reference, an acre is roughly 209 Γ 209 ft if it were square.
How do I convert inches to feet for my measurement?
Divide the inches by 12 and add it to the feet. 8 ft 7 in = 8 + (7 Γ· 12) = 8.58 ft, not 8.7. Getting this wrong introduces an error that compounds through every material estimate downstream.
Do I include closets in square footage?
For material estimates, include them if you're flooring or painting inside them. For real estate listings, closets generally count toward finished living area as long as the space meets ceiling-height requirements β but standards vary by market, so check your local practice.
How do I calculate square footage for walls?
Multiply the room's perimeter by the ceiling height, then subtract windows and doors. A 12 Γ 10 ft room with 8 ft ceilings has a 44 ft perimeter, so 44 Γ 8 = 352 sq ft of wall, minus about 21 sq ft per standard door and 15 per window.
How do I find the square footage of an irregular shape?
Break it into shapes you can calculate β rectangles, triangles, and circles β then add the areas. For genuinely curved areas like garden beds, overlay a grid of rectangles and estimate the partial squares. That's accurate enough for mulch, sod, and gravel.
What is a "square" in roofing?
A roofing square is 100 square feet. A 2,400 sq ft roof is 24 squares. Shingles are sold by the bundle, with three bundles typically covering one square β see our roofing calculator.
Should I measure at the floor or at waist height?
At the floor, wall to wall. Baseboards, bay windows, and walls that aren't plumb all mean a waist-height measurement differs from the actual floor area you're covering.
Estimates for planning only. Quantities are calculated from standard coverage and yield figures and include a waste allowance. Always confirm against the manufacturer figures on the product you buy, and check local requirements before ordering. See our full method and assumptions.