Sqft Calculator
Work out the square footage of any room, wall, yard or lot — in feet, inches, yards or meters. Pick a shape, type your measurements, and get an instant answer with conversions and cost.
To calculate sqft, multiply length by width in feet. A room 20 ft long and 12 ft wide is 20 × 12 = 240 square feet. If you measured in inches, divide each measurement by 12 first, or multiply the inches together and divide by 144. For shapes that are not rectangles, split the space into rectangles, triangles and circles, calculate each part, then add them up.
Formula: Length × Width
Formula: π × Diameter² ÷ 4
Formula: (Base × Height) ÷ 2
Formula: ((Side A + Side B) ÷ 2) × Height
Formula: (Overall area) − (Notch area)
Formula: Outer area − Inner area
How to calculate square footage
Square footage is a measure of area — how much flat surface a space covers. The whole process is three steps, regardless of how complicated the room looks.
- Measure in feet. Run a tape measure along each wall at floor level. If your tape reads in feet and inches, convert the inches to a decimal by dividing by 12 — 12 ft 6 in becomes 12.5 ft. The calculator above has a feet + inches mode that does this for you.
- Apply the formula for the shape. Most rooms are rectangles, so length × width is all you need. Curved and angled spaces use the formulas in the table below.
- Add the parts together. An L-shaped room is just two rectangles. A room with a bay window is a rectangle plus a trapezoid. Work out each piece, then total them.
A worked example, step by step
Here is a real L-shaped living room measured end to end. The trick is to draw a line across the inside corner, turning one awkward shape into two easy rectangles.
Always cross-check. Calculating 20 × 15 = 300 ft² and subtracting the 8 × 6 = 48 ft² notch gives 252 ft² — the same answer. If your two methods disagree, you have mis-measured something.
Square footage formulas
Every measurement goes in as feet, and every answer comes out as square feet.
| Shape | Formula | Example | Result |
|---|---|---|---|
| Square or rectangle | L × W | 20 ft × 12 ft | 240 ft² |
| Circle | π × d² ÷ 4 | 10 ft diameter | 78.54 ft² |
| Triangle | (b × h) ÷ 2 | 20 ft × 9 ft | 90 ft² |
| Trapezoid | ((a + b) ÷ 2) × h | 8 & 12 ft, h 5 ft | 50 ft² |
| L-shape | Total − notch | 300 ft² − 48 ft² | 252 ft² |
| Border or path | Outer − inner | 300 ft² − 176 ft² | 124 ft² |
| Oval / ellipse | π × a × b ÷ 4 | 16 ft × 10 ft | 125.66 ft² |
A fuller reference — including hexagons, parallelograms and irregular lots — is in the square footage formulas by shape guide.
Square foot conversions
Square feet convert cleanly to every other area unit. The one that catches people out is square inches: there are 144 in a square foot, not 12.
| To convert | Do this | Example |
|---|---|---|
| Sq ft → sq inches | × 144 | 10 ft² = 1,440 in² |
| Sq ft → sq yards | ÷ 9 | 90 ft² = 10 yd² |
| Sq ft → sq meters | ÷ 10.7639 | 500 ft² = 46.45 m² |
| Sq ft → acres | ÷ 43,560 | 10,000 ft² = 0.2296 acres |
| Sq meters → sq ft | × 10.7639 | 100 m² = 1,076.39 ft² |
| Acres → sq ft | × 43,560 | 0.5 acre = 21,780 ft² |
Need one specific conversion? Use the sqft to sqm calculator, sqft to acres calculator or sqft to linear feet calculator.
All square footage calculators
Sixteen focused tools, all using the same measurement engine.
Shapes & rooms
Measure any space, whatever shape it is.
Unit conversions
Move between square feet and every other area unit.
Home projects
Work out materials before you order them.
Cost & sizing
Turn square footage into money and equipment size.
Square footage guides
What people use square footage for
Buying and selling property
Price per square foot is the standard way to compare homes of different sizes. Divide the asking price by the finished living area — the price per sqft calculator does it both ways.
Ordering flooring and tile
Measure each room, total it, then add 10% for cuts and waste. The flooring calculator adds the waste factor and converts to boxes.
Painting a room
Wall area, minus doors and windows, divided by 350 sq ft per gallon. The wall and paint calculator handles the openings.
Sizing heating and cooling
Rough AC sizing is about 20 BTU per square foot, and 12,000 BTU is one ton. The BTU and tons calculator works it out.
Frequently asked questions
How do you calculate sqft?
Measure the length and width of the space in feet, then multiply them together. A room 20 feet long and 12 feet wide is 20 × 12 = 240 square feet. For any shape that is not rectangular, split it into rectangles, triangles and circles, work out each piece separately, and add the results.
How do I calculate square footage from inches?
You have two options. Either divide each measurement by 12 to convert it to feet before multiplying, or multiply the inch measurements together and divide the result by 144. Both give the same answer, because 1 square foot contains 144 square inches — not 12.
What is the formula for square footage?
For a rectangle the formula is Length × Width. For a circle it is π × diameter² ÷ 4. For a triangle it is (base × height) ÷ 2. For a trapezoid it is ((side A + side B) ÷ 2) × height. All measurements must be in feet for the answer to come out in square feet.
How many square feet is a 12x12 room?
A 12 by 12 foot room is 144 square feet. Multiply the two sides together: 12 × 12 = 144.
Is this sqft calculator free?
Yes. Every calculator on this site is completely free, needs no sign-up, and works in your browser. Nothing you type is uploaded or stored — all the maths runs on your own device.
How do I convert square feet to square meters?
Multiply square feet by 0.092903 to get square meters, or divide by 10.7639. For example, 500 sq ft × 0.092903 = 46.45 m². The factor is exact because one foot is defined as 0.3048 meters.
How many square feet are in an acre?
One acre is exactly 43,560 square feet. To convert square feet to acres, divide by 43,560. A 10,000 sq ft lot is 10,000 ÷ 43,560 = 0.2296 acres.
Should I include closets and hallways in a room measurement?
For flooring, yes — you will be laying material in them. For a listed house size, standard practice is to include hallways and closets inside the finished living area, but exclude garages, unfinished basements and any space with a ceiling under 7 feet.
Results are estimates for planning purposes. For property listings, appraisals or material orders, confirm measurements on site before committing.