StoreBox's Square Footage Calculator
Rooms, flooring, paint, land. Enter your dimensions in any unit, add as many areas as you need — get total square feet, meters, yards, boxes, and cost instantly.
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How to calculate square footage
Square footage is simply the area of a flat surface — how many one-foot squares would fit inside it. For a rectangular room the math is short: measure the length and the width in feet and multiply them together. A room that is 12 feet long and 10 feet wide is 12 × 10 = 120 square feet. That single multiplication drives almost every flooring order, paint estimate and real-estate listing.
The one rule that trips people up is units: both measurements must be in the same unit before you multiply. If you measure length in feet and width in inches, convert the inches to feet first (divide by 12). The calculator above does this for you — pick feet, inches, yards, meters or centimeters per field and it converts everything to feet behind the scenes, then sums every area you add.
The square footage formula
Most spaces are rectangles, so length × width covers the majority of jobs. When a shape is round — a patio, a rug, a flower bed — use π × radius², where the radius is half the diameter. A circle 10 feet across has a 5 foot radius, so 3.14159 × 5² ≈ 78.54 square feet. For a triangular nook or gable wall, use half the base times the height: a triangle with a 10 foot base and 8 foot height is ½ × 10 × 8 = 40 square feet.
Irregular & L-shaped rooms
Real rooms are rarely a perfect rectangle. The trick is to break the space into simple shapes, calculate each one, and add them together. An L-shaped living-dining room splits cleanly into two rectangles; a room with a bay window is one rectangle plus a half-circle or triangle.
- Draw the room from above and slice it into rectangles, circles and triangles.
- Measure and calculate each piece on its own.
- Add the square footage of every piece for the room total.
That is exactly what the Add another area button does. Add one area per shape, leave each on its own shape setting, and the calculator sums them into a single total — no scratch paper required.
How much flooring, paint or material to buy
Square footage is the start; what you buy needs two more numbers — a waste allowance and the coverage per unit. Cuts, mistakes and pattern-matching mean you should never buy your exact square footage. Add 5–10% for waste on straight-lay flooring and simple paint jobs, and 10–15% for diagonal layouts, busy patterns or rooms with lots of corners.
Once you have the area-plus-waste figure, divide by the coverage on the label and round up:
Example: 540 sq ft of flooring with 10% waste is 594 sq ft. If each carton covers 22.5 sq ft, that is 594 ÷ 22.5 = 26.4 → 27 boxes. Enter the coverage in the calculator's "Coverage / box" field and it does this rounding for you.
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Square feet to square yards, acres & meters
Carpet is often priced by the square yard, land by the acre, and the rest of the world works in square meters. The conversions are fixed, so keep this table handy:
| From square feet | Multiply by | Example: 1,000 sq ft |
|---|---|---|
| Square yards (yd²) | ÷ 9 | 111.11 yd² |
| Square meters (m²) | × 0.092903 | 92.90 m² |
| Acres (ac) | ÷ 43,560 | 0.0230 ac |
| Square inches (in²) | × 144 | 144,000 in² |
| Squares (roofing, 100 sq ft) | ÷ 100 | 10 squares |
The big one to memorize is 9 square feet per square yard — a square yard is 3 ft × 3 ft. And there are 43,560 square feet in an acre, which is the figure you need for lawns, lots and land.
Worked examples
A single room for flooring
A bedroom 12 ft × 15 ft is 12 × 15 = 180 sq ft. With 10% waste that is 198 sq ft; at 22.5 sq ft per box you need 198 ÷ 22.5 = 8.8 → 9 boxes.
A whole apartment
Add three areas: living room 14 × 18 = 252, kitchen 10 × 12 = 120, and a 5 ft-radius round entry = π × 5² ≈ 78.5. Total ≈ 450.5 sq ft — exactly the kind of multi-room sum the calculator handles in one screen.
A lawn in acres
A back yard 80 ft × 60 ft is 4,800 sq ft, which is 4,800 ÷ 43,560 = 0.11 acres — useful for ordering sod, seed or fertilizer that's rated per acre.
Tips before you buy
- Measure twice. A 6-inch error across a big room can throw your order off by several square feet — and one box.
- Always add waste. 10% is the safe default for flooring; go higher for diagonal patterns, herringbone, or rooms with many cuts and closets.
- Buy flooring in full boxes from one batch. Dye lots vary, so getting the box count right the first time avoids a mismatched top-up later.
- Subtract large fixed features only. Skip a kitchen island or a stair opening from floor area, but don't bother deducting small obstacles — the waste allowance covers them.
- Match the unit to the trade. Floors and paint in sq ft, carpet in sq yd, land in acres. The calculator shows all of them at once so you can quote in any of them.
Frequently asked questions
Measure the room's length and width in feet, then multiply them together. A room 12 feet long and 10 feet wide is 12 × 10 = 120 square feet. For odd shapes, split the room into rectangles, calculate each, and add the results.
There are 9 square feet in one square yard, because a square yard is 3 feet by 3 feet (3 × 3 = 9). To convert square feet to square yards, divide by 9.
Calculate the square footage of every room getting flooring and add them up, then add 5–10% for waste and cuts. Divide that total by the square feet per box on the flooring label and round up to get the number of boxes to buy.
A 10 foot by 10 foot room is 100 square feet (10 × 10 = 100).
Measure each interior room's length and width, multiply for each room's square footage, and add them all together. Most listings count finished, heated living space and exclude garages and unfinished basements. The Add another area button above lets you total every room at once.
For a circle, square footage is π × radius², where radius is half the diameter. For a triangle, it is ½ × base × height. Switch the shape selector above to Circle or Triangle and the calculator handles the formula for you.
There are 43,560 square feet in one acre. To convert square feet to acres, divide by 43,560 — useful for lawns, lots and land where materials are priced per acre.
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Disclaimer: This tool is provided by StoreBox for informational purposes only. StoreBox makes no warranties regarding the accuracy of results and is not liable for any losses, damages, or costs arising from reliance on this calculator. Always verify measurements and costs with a qualified professional before ordering flooring, paint, tile or other materials.