Six shapes, not one
Rectangle, L-shaped room, circle, triangle, trapezoid and border areas are all built in, so an odd-shaped living room or a round patio takes one calculation instead of five.
Free area & cost estimator
Square Footage CalculatorMeasure any room, floor, wall or lot in seconds
Enter your measurements in feet, inches, yards or metres and get instant square footage for rectangles, L-shaped rooms, circles, triangles and trapezoids. Add a waste allowance, apply a price per square foot, and stack multiple rooms into one project total.
- 6 room shapes
- Feet & inches supported
- Waste factor + material cost
- No sign-up, no ads in the tool
Square footage calculator tool
1. Choose a shape
Measure wall to wall at the widest point. Round up to the nearest inch rather than down.
2. Waste & cost (optional)
%
/ft²
Flooring and tile installers usually add 10% waste for straight layouts and 15–20% for diagonal or herringbone patterns.
Total area
120square feet
With 10% waste allowance: 132 ft² · Estimated cost: —
11.15square metres
13.33square yards
17,280square inches
0.0028acres
3. Project total
No rooms added yet. Measure a space above, then add it here to build a whole-house square footage total.
Project total0 ft²
Results update as you type.
Why this square feet calculator does more than the rest
Most square footage tools give you one box for length, one for width and nothing else. Real rooms have alcoves, bay windows, round patios and skirting. This calculator handles them — and then tells you what the material will cost.
Feet and inches, properly
Tape measures do not read in decimals. Switch to feet & inches mode and enter 12 ft 7 in exactly as you measured it — no converting fractions in your head first.
Waste factor and cost built in
Add a 10–20% overage allowance and a price per square foot to turn raw area into a realistic material budget before you walk into the store.
Whole-house totals
Add each room to a running project list and get the combined square footage of a house, apartment or floor — the number quotes, listings and appraisals actually ask for.
Instant unit conversions
Every result is shown in square feet, square metres, square yards, square inches and acres at the same time, so you can quote an international supplier without a second tool.
Fast, private, mobile-first
Everything runs in your browser with no libraries, no accounts and no data sent anywhere. It loads and calculates on a phone standing in an empty room with one bar of signal.
How to calculate square footage of a room
Square footage is simply length multiplied by width, measured in feet. The accuracy comes from how you measure, not from the maths.
Measure the longest wall
Run the tape wall to wall at floor level, not at worktop height. Note the measurement in feet and inches and round up to the nearest inch.
Measure the width the same way
Measure at right angles to the first wall. If opposite walls differ, use the larger figure so you never order short.
Split irregular rooms
Break an L-shaped or bay-window room into rectangles, use the L-shaped mode for the two main sections, and add any remaining alcove as its own entry.
Add waste, then price it
Apply a 10% allowance for straight-lay flooring or 15–20% for diagonal patterns, enter your price per square foot, and add each room to the project total.
Square footage formulas by shape
Every measurement is converted to feet first, so the result always lands in square feet no matter which unit you entered.
| Shape | Formula | Typical use |
|---|---|---|
| Rectangle or square | length × width | Bedrooms, kitchens, decks, walls, plots |
| L-shaped room | (L1 × W1) + (L2 × W2) | Open-plan living and dining areas |
| Circle | π × (diameter / 2)² | Round patios, fire pits, rugs, pools |
| Triangle | (base × height) / 2 | Gable walls, corner sections, roof faces |
| Trapezoid | ((a + b) / 2) × height | Tapered gardens, angled driveways |
| Border or frame | outer area − inner area | Pool surrounds, path edging, tile borders |
Useful constants: 1 square yard = 9 ft², 1 square metre = 10.7639 ft², 1 acre = 43,560 ft², and 1 ft² = 144 square inches.
Where a square footage calculator saves you money
Area is the unit almost every home cost is quoted in, so a five-minute measurement changes what you pay.
Flooring, tile and carpet
Order by the box, not by guesswork. Knowing the exact area plus waste keeps you from a second delivery charge or a dye-lot mismatch.
Paint and wallpaper
Calculate wall area instead of floor area, subtract doors and windows using the border mode, and buy the right number of tins first time.
Rent and property listings
Compare price per square foot between listings to see which one is actually the better deal — then sanity-check the budget with a rent affordability calculator.
Buying and renovating
Cost per square foot is the fastest way to compare contractor quotes. Pair it with a mortgage calculator when you are pricing a purchase plus works.
Lawn, mulch and turf
Seed, fertiliser and mulch are all sold by coverage area. Measure the lawn once and you stop over-buying every spring.
Working in metric
Suppliers quoting in square metres are one glance away, and our unit converter handles anything else the project throws at you.
Square footage calculator FAQs
The questions people ask most when measuring a room, a house or a job.
How do I calculate square footage?
Measure the length and width of the space in feet and multiply them together. A room 12 ft long and 10 ft wide is 12 × 10 = 120 square feet. If you measured in inches, divide each measurement by 12 first; if you measured in metres, multiply the final area by 10.7639.
How do I calculate the square footage of a room that is not a rectangle?
Split it into simple shapes and add the areas together. For an L-shaped room, use the L-shaped mode and enter the length and width of each rectangular section. For bay windows, alcoves or curved patios, calculate each part separately and add every piece to the project list to get one combined total.
How much waste should I add for flooring or tile?
Add about 10% for a straight layout in a simple rectangular room, 15% for a room with lots of cuts around cabinets or corners, and 15–20% for diagonal, herringbone or large-format tile. Patterned material that needs matching may need more. The waste field applies your percentage to the area instantly.
How many square feet are in a square yard or a square metre?
One square yard is 9 square feet and one square metre is 10.7639 square feet. Going the other way, divide square feet by 9 for square yards or multiply by 0.092903 for square metres. An acre is 43,560 square feet. The calculator shows all of these conversions alongside every result.
Does square footage include closets, hallways and the garage?
For listings, gross living area normally includes finished, heated spaces such as closets, hallways and stairwells, but excludes garages, unfinished basements, attics and open porches. Rules vary by region and appraiser, so measure each space separately, label it in the project list and you can include or exclude it later without remeasuring.
How do I calculate price per square foot?
Divide the total price by the total square footage. A $2,400 flooring quote for a 400 ft² room works out at $6 per square foot. To go the other way, enter your price per square foot in the calculator and it multiplies it by the area including your waste allowance to give an estimated material cost.
How do I measure square footage for painting walls?
Measure the height and length of each wall and multiply them, then add the walls together. Use the triangle mode for gable ends. Subtract roughly 20 ft² for each door and 15 ft² for each average window, or use the border mode to take an opening out of a wall exactly. Most paint covers 350–400 ft² per gallon per coat.
Is this square footage calculator free and accurate?
Yes. It is completely free, needs no sign-up and runs entirely in your browser, so nothing you measure is uploaded. The maths uses standard geometric formulas with full floating-point precision and only rounds for display, so results are as accurate as the measurements you enter.
Measure once, order right
Whether you are pricing flooring, comparing listings by price per square foot or working out how much paint a gable wall needs, get the number right before you spend. Scroll back up, enter your measurements and build your project total in under a minute.