Measure the area of a rectangle, circle or triangle in square feet, square yards, square metres and acres.
Square Footage Calculator
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Results
Area
384.00 ft²
A = length × width
Calculated with BuildCalculators.com
Square footage is the multiplication everyone knows — length times width — and yet it is where a surprising number of estimates go wrong, because real spaces are rarely one clean rectangle. The method that works every time: break the space into shapes you can calculate, work each one out, and add them up.
This calculator handles the three shapes that cover nearly every case. A rectangle covers rooms, slabs and driveways. A circle covers pools, tanks and round patios. A triangle covers gables, corner lots and the odd cut-off that is left when you split an irregular plan into rectangles.
A = length × widthA = π × r², where r is half the diameterA = ½ × base × heightyd² = ft² ÷ 9m² = ft² ÷ 10.764acres = ft² ÷ 43,560A tape measure says 24 ft 6 in, but the formula needs 24.5 — the inches divided by 12, not tacked on after a decimal point. Writing 24 ft 6 in as 24.6 is the most common measuring error there is, and it overstates a 16 ft wide room by more than a square foot per inch of error. Divide the inches by 12 first: 6 ÷ 12 = 0.5, so 24 ft 6 in is 24.5 ft.
Because that is what you can measure. Nobody finds the exact centre of a round pool to measure a radius; you pull the tape across the widest point. The calculator halves the diameter for you, which also removes the classic error of squaring the diameter instead of the radius — a mistake that inflates the answer four-fold.
Split it along imaginary lines into rectangles and triangles, calculate each piece, and add them. An L-shaped room is two rectangles. A five-sided lot is a rectangle plus a triangle. There is no shape a tape measure can survey that this method cannot handle — the only skill is choosing where to draw the lines, and the fewest lines usually means the fewest mistakes.
Flooring and carpet are often priced per square yard — nine square feet, a square three feet on each side. Metric drawings and imported materials use square metres, at 10.764 square feet each. Land uses acres, at 43,560 square feet — roughly a square 209 ft on a side. The calculator shows all three so the same measurement works for whichever quote you are reading.
The simple case, done properly: one rectangle, measured in feet.
384 square feet
For flooring, add the supplier’s cutting waste on top — typically 5–10% for planks and tile, more for patterned material that must be matched.
A 24 × 16 ft living room with a 10 × 8 ft alcove off one side.
464 square feet
Split along the line where the alcove meets the room. Any L-shape splits into exactly two rectangles — if you find yourself with three, the lines are in the wrong place.
A circular above-ground pool, measured across the widest point.
About 452 square feet
Squaring the diameter by mistake gives 1,810 ft² — four times too much. If a circle result looks enormous, that is almost always what happened.
The triangle at the top of a wall: 28 ft across the base, rising 7 ft to the peak.
98 square feet
The height is measured vertically from the base line to the peak — not along the sloping edge. Measuring the slope instead overstates every gable.
Raw area — add cutting or coverage waste per material.
| Space | Dimensions | Square feet | Square yards |
|---|---|---|---|
| Small bedroom | 10 × 12 ft | 120 ft² | 13.3 yd² |
| Single garage bay | 12 × 20 ft | 240 ft² | 26.7 yd² |
| Two-car garage | 24 × 24 ft | 576 ft² | 64 yd² |
| Standard driveway | 20 × 20 ft | 400 ft² | 44.4 yd² |
| Long driveway | 60 × 12 ft | 720 ft² | 80 yd² |
| Quarter-acre lot | — | 10,890 ft² | 1,210 yd² |
| From | To | Do this |
|---|---|---|
| Square feet | Square yards | Divide by 9 |
| Square feet | Square metres | Divide by 10.764 |
| Square feet | Acres | Divide by 43,560 |
| Square yards | Square feet | Multiply by 9 |
| Square metres | Square feet | Multiply by 10.764 |
| Feet + inches | Decimal feet | Divide the inches by 12, then add |
Added to the measured area when ordering — cutting scrap, breakage and pattern matching.
| Material | Typical allowance |
|---|---|
| Carpet | 5–10% |
| Laminate or plank flooring | 5–10% |
| Tile, straight layout | 10% |
| Tile, diagonal or patterned | 15–20% |
| Sod | 5–10% |
| Paint | None — divide area by coverage per gallon |
Area itself costs nothing — but nearly everything a contractor quotes is priced from it, which makes an accurate square footage the difference between comparing quotes and guessing between them.
The figures below are national US planning ranges for 2026, installed unless stated. They move with material prices and local labour; use them to sanity-check a quote, not to write one.
Carpet typically runs $2–$8 per square foot installed, laminate and vinyl plank $3–$10, hardwood $8–$18, and tile $10–$25 with the wide range driven by the tile itself and the layout. Note that carpet is often quoted per square yard — multiply a per-yard price by 9 to compare it against per-foot quotes on equal terms.
A broom-finish concrete slab installs at roughly $6–$12 per square foot including base and labour; asphalt paving at $5–$10. Both are covered in detail by their own calculators on this site, which also itemise the base and removal costs that a per-square-foot figure hides.
Exterior painting typically quotes at $2–$5 per square foot of wall area — which is where gable triangles and the feet-and-inches conversion earn their keep, because wall area is the sum of rectangles and triangles, not the floor plan. Interior painting runs $2–$6 per square foot of floor area as a rough proxy.
Sod installs at $1–$2 per square foot; artificial turf at $9–$20. Landscape quotes lean heavily on area, and a lot measured to the nearest hundred square feet is usually accurate enough — the quarter-acre figure in the table above is more precision than most yard projects need.
A contractor buys material for your area plus cutting waste, and some trades round up to the next full unit — a box of flooring, a roll of carpet, a square of roofing. A quote a few percent above your measured area is normal. One 25% above it deserves a question.
Inches are twelfths, not tenths. 24 ft 6 in is 24.5 ft, and the half-inch-sized errors this habit produces compound across every dimension of every room. Convert the inches first — divide by 12 — then multiply.
The formula squares the radius. Squaring the diameter gives exactly four times the true area, which turns a 452 ft² pool surround into an 1,810 ft² materials order. This calculator asks for the diameter and halves it internally so the error cannot happen.
A floor plan shows horizontal area. A gable, a ramp or a pitched roof is larger than its footprint — a roof by 12% to 40% or more depending on pitch. For roofs, use the roofing calculator, which applies the pitch multiplier properly rather than leaving it to judgement.
For flooring, a kitchen island or a stair opening genuinely reduces the area to cover, and is worth subtracting. A doorway or a heating vent does not. The rule: subtract anything you could not physically lay material on that is bigger than about a square yard, and ignore the rest — the waste allowance absorbs it.
Measure true area first and record it. Apply the waste percentage only when ordering a specific material, because the right allowance is a property of the material — 5% for carpet, 20% for diagonal tile — not of the room. An area figure with waste already baked in is useless the next time you need it.
Round at the end, not along the way. Rounding six rooms up to the nearest 10 ft² each can add a spurious 50 ft² to a whole-house total — enough to buy a box of flooring you did not need. Carry the decimals through the addition and round the final figure once.
Multiply length by width in feet. A 24 by 16 ft room is 384 square feet. For a room that is not rectangular, split it into rectangles, work out each one, and add them together.
Nine. A square yard is 3 ft by 3 ft. To convert square feet to square yards, divide by 9 — flooring and paving are often priced this way.
Area equals π times the radius squared, where the radius is half the diameter. A 24 ft circle has a 12 ft radius, so the area is π × 144, or about 452 square feet.
43,560 square feet. That is roughly a square 209 ft on each side.
Embed the Square Footage Calculator anywhere — it is free, stays in sync with this page, and sizes itself to fit. The only condition is the credit line in the snippet, which links your readers to the full version with the formulas and worked examples.
This calculator uses published constants from named industry sources, each asserted in an automated test that runs on every build. The formula is printed with the result above, and any correction we make is logged on the changelog.
It is a planning estimate. It does not replace an engineer, a site visit or a written quote — confirm quantities with your supplier before ordering.