A square footage calculator works out the area of a floor, wall, yard or roof section so you can order material and price the job. For a rectangle, square footage is length × width in feet: a 12 × 10 ft room is 120 sq ft. Contruva’s free square footage calculator does that for every area on the job at once, including L-shapes, triangles, circles and trapezoids, then gives you the total in square feet, square metres and square yards.
Open the free square footage calculator in your browser. No login, no email, nothing to pay.
Open the free toolIt takes feet and inches or metres, lets you subtract areas you won’t cover (a kitchen island, a stairwell, a hot tub pad), adds a waste percentage, and multiplies by your price per square foot or square metre. No login and no email. Below are the formulas it uses, with worked examples you can check by hand.
How to use the square footage calculator
Imperial takes feet plus inches for every measurement. Metric takes metres, so 3 m 60 cm is 3.6.
Name it (living room, hallway, front bed), pick the shape and enter the measurements the shape needs.
Three identical bedrooms are one area with a quantity of 3. Set an island or stairwell to Subtract to take it out of the total.
Waste is the overage you buy for cuts and offcuts. The price is what you charge per sq ft (or per m² in metric).
Total sq ft, m² and sq yd, the area with waste, each area’s share, and the price on both the net area and the area with waste.
The calculator shows two prices on purpose. Labour is usually priced on the net area you actually install, cover or clean. Material is bought on the area with waste, because you pay for the offcuts too.
How do you calculate square footage?
Measure the length and the width in feet and multiply them. The answer is in square feet. If a space isn’t a rectangle, split it into shapes you can measure, work out each one, add them together, and subtract anything inside the space you won’t be covering.
Here is the default example in the calculator: an open-plan main floor where the customer wants new flooring in the living room and kitchen, but not under the island.
| Area | Measurements | Square feet |
|---|---|---|
| Living room | 18 ft × 14 ft 6 in (14.5 ft) | 261 |
| Kitchen | 12 ft × 11 ft | 132 |
| Island (subtract) | 6 ft × 3 ft 6 in (3.5 ft) | −21 |
| Net area | 372 sq ft |
261 + 132 − 21 = 372 sq ft, which is 34.56 m² or 41.33 sq yd.
372 × 1.10 = 409.2 sq ft with 10% waste.
At $4.50 per sq ft: 372 × $4.50 = $1,674. On the area with waste it’s 409.2 × $4.50 = $1,841.40.
Converting feet and inches to decimal feet
Tape measures read in feet and inches, but the math needs one unit. Divide the inches by 12 and add them to the feet: 6 ft 9 in is 6 + 9 ÷ 12 = 6.75 ft. The calculator does this for every measurement, so you can type what the tape says.
| Inches | Decimal of a foot | Inches | Decimal of a foot |
|---|---|---|---|
| 1 | 0.083 | 7 | 0.583 |
| 2 | 0.167 | 8 | 0.667 |
| 3 | 0.25 | 9 | 0.75 |
| 4 | 0.333 | 10 | 0.833 |
| 5 | 0.417 | 11 | 0.917 |
| 6 | 0.5 | 12 | 1.0 |
The classic error is writing 12 ft 6 in as 12.6 ft. It’s 12.5 ft. On a 12 ft 6 in × 10 ft 9 in room the right answer is 12.5 × 10.75 = 134.4 sq ft; using 12.6 × 10.9 gives 137.3 sq ft, and that kind of mistake repeats on every room in the house.
Area formulas for every shape
Every shape in the calculator uses a standard geometry formula. Measure in feet (or metres) and the result is in square feet (or square metres).
| Shape | What to measure | Formula | Example |
|---|---|---|---|
| Rectangle or square | Length and width | Length × width | 12 × 10 ft = 120 sq ft |
| L-shape | Overall length and width, plus the missing corner | Overall rectangle − missing corner | (20 × 16) − (8 × 6) = 272 sq ft |
| Triangle | Base and height (at right angles to the base) | Base × height ÷ 2 | 10 × 8 ÷ 2 = 40 sq ft |
| Circle | Diameter, edge to edge through the centre | π × diameter² ÷ 4 | 12 ft across = 113.1 sq ft |
| Trapezoid | The two parallel sides and the depth between them | (side A + side B) ÷ 2 × depth | (20 + 14) ÷ 2 × 10 = 170 sq ft |
The calculator asks for a circle’s diameter rather than its radius because that’s what you can actually measure across a patio, a round bed or a gazebo floor. For a half circle (a bay or a curved bed edge), add a circle with a quantity of 0.5.
The height of a triangle is measured square to the base, not along the sloped side. For an angled corner in a room, the base and height are usually the two walls that meet at the right angle.
How to measure an irregular room
Almost no room is a perfect rectangle. Closets, bump-outs, angled walls and bay windows all change the number. The fix is the same every time: sketch the floor, split it into simple shapes, and measure each one.
A rough sketch on the back of a work order is enough. Mark every wall, closet and opening.
Most rooms split into two or three rectangles. Use a triangle or trapezoid only for angled walls.
Measure the actual floor, not the baseboard top, and take the longer reading if walls aren’t parallel.
Islands, built-in cabinets, stairwells, fireplaces and tubs go in as Subtract areas.
If the total is bigger than the overall outside dimensions multiplied together, a piece was counted twice.
An L-shaped room can be done two ways: two rectangles added together, or one big rectangle minus the missing corner. The calculator’s L-shape uses the second method, which needs only four measurements. Both give the same answer when the measurements are right, so use whichever is easier to measure on site.
Square feet to square metres and square yards
Canadian jobs come in both units. Plans and some suppliers use metric while most tape measures, flooring boxes and customers still talk in square feet. One foot is exactly 0.3048 m, so:
| To convert | Multiply by | Example |
|---|---|---|
| Square metres to square feet | 10.7639 | 15.12 m² × 10.7639 = 162.75 sq ft |
| Square feet to square metres | 0.0929 | 372 sq ft × 0.0929 = 34.56 m² |
| Square feet to square yards | ÷ 9 | 372 sq ft ÷ 9 = 41.33 sq yd |
| Square yards to square feet | 9 | 10 sq yd × 9 = 90 sq ft |
In metric mode the calculator takes metres and prices per square metre. A 4.2 × 3.6 m room is 15.12 m², which is 162.75 sq ft. At $45 per m² that’s 15.12 × $45 = $680.40. Square yards still turn up for carpet and some sod and landscape fabric, so the calculator shows them too.
Pricing a job per square foot
Plenty of trades quote by area. Square footage is the base unit; what changes is what you measure and whether you add waste.
| Trade | What you measure | Waste? |
|---|---|---|
| Flooring | Floor area of each room, minus islands and built-ins | Yes, on material; labour on the net area |
| Painting | Wall and ceiling area, or floor area for whole-room pricing | Not on area; coverage is handled in paint quantity |
| Cleaning | Finished floor area | No |
| Landscaping: sod, mulch, fabric | Lawn or bed area, including curves and circles | Yes, for cuts along beds and edges |
| Drywall and insulation | Wall and ceiling area | Yes, on material |
| Patios and slabs | Surface area, then depth for volume | Yes, on material |
The square footage calculator gives you the area and the price at one rate. For the material count on top of that area (boxes of flooring, gallons of paint, sheets of drywall, yards of concrete) use the construction material calculator. For hardscapes and roofs, the paver calculator and roofing calculator handle the pattern, slope and squares.
Waste factors depend on the product and the layout, so follow the manufacturer’s guidance. Straight-lay flooring in a plain rectangle needs the least; diagonal and herringbone layouts, small rooms and lots of doorways need more. Price per square foot is also only as good as the costs behind it. Work out your labour rate with the hourly rate calculator and check your margin in the markup calculator before you settle on a per-foot number.
Measuring mistakes to avoid
- Writing inches as decimals. 10 ft 9 in is 10.75 ft, not 10.9. Enter feet and inches separately and let the calculator convert.
- Counting a piece twice. When you split a room, the shapes must not overlap. Check the total against the overall outside size.
- Forgetting closets and hallways. They’re small, but they add up across a whole house and they’re where the cuts are.
- Not subtracting islands, tubs and stairwells. Or subtracting them when the customer wants flooring under the fridge and stove.
- Pricing labour on the area with waste. The customer pays for the floor you install. The offcuts are a material cost.
- Measuring at the ceiling. Walls aren’t always plumb. Measure where the material goes.
From square footage to a quote
Once you have the area, the quote is area × your rate for each line, plus materials, plus anything that isn’t priced by area: removal and disposal, stairs, trim, transitions and moving furniture. The free estimate generator turns those lines into a clean PDF estimate.
If you quote area-priced work every week, Contruva keeps your per-square-foot and per-square-metre prices in a price catalog, so measured areas go straight onto a quote with your markup. Customers sign on their phone and pay the deposit, and the quote becomes the invoice with online payments when the job is done. Everything is in one plan, Contruva Pro, at $249.99 CAD a month. Try it free for 7 days, no credit card needed.