Square Footage Calculator
0 ft²
To calculate square footage, multiply length by width in feet: a 12' 6" × 10' room is 12.5 × 10 = 125 ft². Divide square feet by 9 for square yards and by 43,560 for acres (NIST Handbook 44). For an odd shape, add rectangles, circles and triangles in the square footage calculator, and subtract cutouts.
The tool above is a square feet calculator built from rows. Each row is a Rectangle, Circle or Triangle with its own Quantity and a + or − sign. An L-shaped room, three bedrooms, a wall minus its door and windows: each comes out as one number. Press + Add area for the next row.
Sizes go in the way the tape reads them. 12' 6 1/2" fits in one field, down to 1/16, and a bare 12 6 reads as 12 ft 6 in, not as one big number. That's where most sq ft calculator mistakes start. It's a free online square footage calculator, no sign-up.
How to calculate square footage
Measure the length and the width in feet and multiply them:
length (ft) × width (ft) = square feet (ft²)
The 12' 6" × 10' room: 6 inches is half a foot, so 12.5 × 10 = 125 ft². Enter it as one Rectangle row and the display reads 125 ft².
A countertop works the same way, so this doubles as a square footage calculator for countertops: give each straight run of counter its own Rectangle row and the total adds up. Any square foot calculator does this multiplication; the rows are what save you the scratch paper.
Feet and inches
This is a square footage calculator with feet and inches: type 12' 6" and the field turns it into 12.5 ft before it multiplies. No converting by hand first. Feet in, square feet out, which is all a ft to sq ft calculator has to do.
Measured in inches only? Type 150" and 120" with the inch mark. No separate square footage calculator inches mode needed: 150" × 120" = 18,000 in², and 18,000 ÷ 144 = 125 ft². One square foot is 12 in × 12 in, or 144 in², the figure in NIST Handbook 44. Same room, same 125 ft².
Circles and triangles
Pick Circle for anything round and enter the Diameter, measured straight across. The math is π × radius², where the radius is half the diameter. A 10' circle is π × 5² = 78.54 ft², shown as 78.5 ft². A round patio, a fire pit area, the top of a round pool: the circle square footage calculator covers all three. Looking for a pool square footage calculator? Measure across the water.
Pick Triangle for a corner bed or a gable end: Base and Height, and the area is ½ × base × height. Base 10', height 6': ½ × 10 × 6 = 30 ft². The height is measured square to the base, not along the sloped side. Nothing else goes into the triangle square footage calculator.
Square footage of a room
How to calculate square feet of a room: measure the length and the width wall to wall, then multiply. Rooms that aren't a plain box get split into rectangles. In the room square footage calculator above, that's one row per piece.
An L-shaped room is two rows. Say one part is 12' × 10' and the other 6' × 4': 120 + 24 = 144 ft². A fireplace hearth or a built-in you want to leave out goes in as a − row.
Measuring the whole floor? Add a row for each room, and if several rooms are the same size, enter one and set Quantity. That's the square footage calculator for multiple rooms: every row adds to one total.
| Room | Square feet |
|---|---|
| 10' × 10' | 100 ft² |
| 10' × 12' | 120 ft² |
| 12' × 12' | 144 ft² |
| 12' × 14' | 168 ft² |
| 12' 6" × 10' | 125 ft² |
Square footage of a house
How to calculate square feet of a house with this tool: measure every room, enter each as a row, and read the total. Used as a house square footage calculator, it adds what you measured and nothing else.
For a listing or appraisal, homes are measured by the ANSI Z765 standard; this calculator adds up the rooms you measure.
Square footage of a wall
How to calculate square feet of a wall: length × height, minus doors and windows. Here it's one calculation with + and − rows.
Take a 12' × 14' room with 8' walls. Around the room, 12 + 14 + 12 + 14 = 52 ft of wall:
+52' × 8' = 416 ft²−door 3' × 6' 8" = 20 ft²−window 3' × 5',Quantity2 = 30 ft²
416 − 20 − 30 = 366 ft². Those door and window sizes are examples; measure your own. If the − rows add up to more than the + rows, the display shows Cutouts are larger than the area instead of a result.
The wall square footage calculator stops at square feet. For gallons, take the 366 ft² to the paint calculator.
Square feet to acres and square yards
Square feet to acres: divide by 43,560. NIST Handbook 44 lists 1 acre = 43,560 square feet, so an acre laid out as a square is about 209 ft on each side. You don't need a separate square footage to acres calculator: the acres line sits on the display under every result. The 125 ft² room is 0.0029 acres.
Square feet to square yards: divide by 9, because a yard is 3 ft and 3 × 3 = 9 ft² (NIST Handbook 44 again). The same room is 125 ÷ 9 = 13.9 yd².
Square meters are on the display too. One foot is exactly 0.3048 m, so 1 ft² = 0.09290304 m², and the room is 11.6 m². Switch the site to metric and the fields take meters.
For a yard or a lot, add it as rows and subtract the house, the driveway, the patio. What's left is the grass area for seed or sod, so the same rows make a lawn square footage calculator. Covering part of it with stone? Take the number to the gravel calculator, which has an Area input for it.
What's next
Press Add to project under the result. The area goes to My project as a note line, Area 125 ft². Tap the name to rename it, for example Living room 125 ft². Lines from other calculators sit in the same list, so the room area can be next to the gallons of paint and the tons of gravel, and you can print it. The numbers you enter stay in your browser; no account needed.
The area doesn't carry over on its own: type it into the next calculator.
- Painting the walls: paint calculator.
- Stone for a path or a pad: gravel calculator.
- Area × depth for topsoil, mulch or fill: cubic yard calculator.
- An odd-shaped slab: get the area here, then the concrete on the concrete slab calculator.
FAQ
How do I calculate the square footage of my home?
Measure each room, enter it as a Rectangle row (two rows for an L-shape) and read the total. Rooms of the same size can share one row with Quantity.
Why divide by 144 for square footage?
A square foot is 12 in × 12 in, which is 144 in² (NIST Handbook 44). Dividing square inches by 144 gives square feet: 150" × 120" = 18,000 in², and 18,000 ÷ 144 = 125 ft².
What is 12 ft by 8 ft in square feet?
96 ft². 12 × 8 = 96.
How many square feet is a 10x10 room?
100 ft². 10 × 10 = 100.
How many square feet in an acre?
43,560, the figure NIST Handbook 44 gives. As a square, that's about 208.7 ft on each side.
Results are only as exact as your measurements. Measure twice before you order material.