Square Footage Calculator
Measure the area of any room, floor, or outdoor space — even an L-shaped or round one — and get the total in square feet, square yards, and square metres.
Areas to measure
Results
2 areas added give a total of 168 square feet (18.7 sq yd, 15.6 m²).
Total area
168 sq ft
That's a typical single-room area — the range of most bedrooms, kitchens, and living rooms.
This figure is the net area only. Material calculators add a separate waste allowance on top of it, so don't pad this number yourself and then add waste again.
Square yards: 18.7 sq yd
Square metres: 15.6 m²
How this works
Every shape is reduced to its own exact area formula, the areas marked "add" are summed, and any areas marked "subtract" are taken away. Dimensions are converted to metres the moment you type them, the total is computed once in square metres, and that single figure is then shown in square feet, square yards, and square metres, so the three results always agree with each other. The conversions use the exact legal definitions: 1 foot is exactly 0.3048 m, 1 inch is exactly 2.54 cm, and 1 yard is exactly 3 feet, which makes 1 square yard exactly 9 square feet and 1 square foot exactly 0.09290304 m² (NIST Special Publication 811, Guide for the Use of the International System of Units).
- Rectangle or square: Area = length × width
- Circle: Area = π × (diameter ÷ 2)², with π ≈ 3.14159
- Half circle: Area = π × (diameter ÷ 2)² ÷ 2
- Triangle: Area = ½ × base × height
- Trapezoid: Area = ½ × (side A + side B) × height
For the triangle and the trapezoid, "height" is the perpendicular distance: a line at a right angle to the base (or between the two parallel sides), not the length of a sloping edge. Measuring along the slanted edge is the most common way a triangle area comes out too big.
How to calculate square footage by hand
- Sketch the space from above on paper. It doesn't need to be to scale, but every wall or edge should appear.
- Split the sketch into simple shapes. Most rooms are one rectangle; an L-shaped room is two rectangles; a bay window is a rectangle plus a trapezoid; a round patio is a circle.
- Measure each shape along the floor (or ground), wall to wall, and write each dimension on the sketch. Measure to the nearest inch — or the nearest centimetre — then stay in one unit.
- Convert mixed feet and inches to decimal feet before multiplying: divide the inches by 12. 10 ft 6 in is 10.5 ft; 12 ft 3 in is 12.25 ft.
- Work out each shape's area with its formula, then add the pieces together. Subtract anything you aren't covering, such as a kitchen island or a fireplace hearth.
- Convert the total if you need another unit: divide square feet by 9 for square yards, or multiply by 0.0929 for square metres.
Square feet, square yards and square metres: conversion table
Common room and project sizes with their exact equivalents. Square yards are exact (divide by 9); square metres are rounded to two decimals.
| Square feet | Square yards | Square metres | Typical space |
|---|---|---|---|
| 25 sq ft | 2.78 sq yd | 2.32 m² | 5 × 5 ft closet or landing |
| 50 sq ft | 5.56 sq yd | 4.65 m² | 5 × 10 ft bathroom |
| 100 sq ft | 11.11 sq yd | 9.29 m² | 10 × 10 ft room |
| 144 sq ft | 16.00 sq yd | 13.38 m² | 12 × 12 ft bedroom |
| 200 sq ft | 22.22 sq yd | 18.58 m² | 10 × 20 ft room |
| 300 sq ft | 33.33 sq yd | 27.87 m² | 15 × 20 ft living room |
| 400 sq ft | 44.44 sq yd | 37.16 m² | 20 × 20 ft two-car garage |
| 500 sq ft | 55.56 sq yd | 46.45 m² | 20 × 25 ft open-plan area |
| 1,000 sq ft | 111.11 sq yd | 92.90 m² | small apartment floor |
| 2,000 sq ft | 222.22 sq yd | 185.81 m² | average single-family house |
- 1 sq ft = 144 sq in = 0.1111 sq yd = 0.0929 m²
- 1 sq yd = 9 sq ft = 0.8361 m²
- 1 m² = 10.7639 sq ft = 1.1960 sq yd
- 1 acre = 43,560 sq ft = 4,840 sq yd ≈ 4,046.86 m²
Worked example: an L-shaped living room
An L-shaped living and dining room measures 20 ft along its long wall. Rather than guessing one overall size, split it at the inside corner into two rectangles. The main section is 20 ft × 12 ft = 240 sq ft. The dining leg that sticks out is 10 ft 6 in × 8 ft; 6 inches is 0.5 ft, so that is 10.5 × 8 = 84 sq ft. The total is 240 + 84 = 324 sq ft. In square yards that is 324 ÷ 9 = 36 sq yd, and in square metres 324 × 0.0929 ≈ 30.1 m². Had the room been measured as one 20 ft × 20 ft box, the answer would have been 400 sq ft — 76 sq ft (23%) too high, because the missing corner would have been counted as floor. At $4.50 per sq ft for a finish, that single-rectangle shortcut would have overstated the cost by $342.
Second example: a round patio with a planter cut-out
A circular patio is 14 ft across. Its area is π × (14 ÷ 2)² = 3.14159 × 49 ≈ 153.9 sq ft. In the middle sits a square planter, 3 ft × 3 ft, that won't be paved, so it is entered as a subtracted rectangle: 153.9 − 9 = 144.9 sq ft, or about 16.1 sq yd and 13.5 m². If the same patio were measured in metres (4.27 m across), the calculator returns the same 13.5 m², because every unit is converted to the same base before the shapes are combined.
Common mistakes
Adding feet and inches as if they were decimals
12 ft 6 in is 12.5 ft, not 12.6 ft. Typing 12.6 overstates every row of that room by 0.1 ft, and on a 12.5 × 20 ft room it adds 2 sq ft. Either convert inches to decimal feet (inches ÷ 12) or switch the calculator to inches and enter 150.
Using a sloped edge as a triangle's height
The height of a triangle or trapezoid is measured at a right angle, not along the diagonal side. For a triangular corner with a 10 ft base and a 7 ft sloping side, the true height might be only 5 ft — 25 sq ft rather than 35.
Converting square feet to square yards by dividing by 3
A yard is 3 feet, but a square yard is 3 × 3 = 9 square feet. Dividing 144 sq ft by 3 gives 48, which is three times the correct 16 sq yd. The same trap applies to metres: 1 m² is 10.76 sq ft, not 3.28.
Measuring one overall box for an irregular room
Taking the longest length and the widest width of an L-shaped or angled room counts floor that isn't there. Split the space into its real shapes and add them, as in the worked example above.
Padding the measurement and then adding waste again
Measure the true area here. Material calculators add their own waste percentage for cuts; if you round every dimension up by a foot first, you pay for waste twice.
Edge cases
- Out-of-square rooms: if the two opposite walls differ in length by more than an inch or two, measure both and treat the room as a trapezoid (the two wall lengths are the parallel sides, the room's depth is the height).
- Curved walls and bay windows: approximate a shallow curve as a trapezoid. For a true half circle, the area is half of the full circle: a 6 ft half-round bay is π × 3² ÷ 2 ≈ 14.1 sq ft. Choose the half-circle shape and enter the straight edge as the diameter.
- Stairs are not a floor area in this sense: each tread and riser is a separate small rectangle; measure one of each and multiply by the number of steps.
- Sloped surfaces such as a roof or a ramp: this calculator gives flat, plan-view area. A pitched roof's surface is larger than its footprint — use the roof pitch tools for that.
- Walls and ceilings: the math is the same (a wall is length × height), but paint and drywall calculators already subtract doors and windows for you.
FAQ
How do I calculate square footage?
Multiply length by width for a rectangular space, both in feet: a 12 ft × 15 ft room is 180 sq ft. For any other shape, split it into rectangles, triangles, circles, or trapezoids, work out each one's area, and add them together. If you measured in inches, divide the result by 144 to get square feet.
How do I convert square feet to square yards?
Divide square feet by 9. There are 3 feet in a yard, so a square yard is 3 ft × 3 ft = 9 sq ft. For example, 270 sq ft ÷ 9 = 30 sq yd. To go back, multiply square yards by 9.
How do I convert square feet to square metres?
Multiply square feet by 0.092903, or divide by 10.7639. A 200 sq ft room is about 18.58 m². To convert square metres to square feet, multiply by 10.7639.
What is the difference between square feet and linear feet?
Linear feet measure length along a single line — the run of a baseboard, a fence, or a countertop edge. Square feet measure a surface: length times width. A 10 ft × 10 ft room has 100 sq ft of floor but 40 linear feet of wall around it. Trim, fencing, and edging are sold by linear foot; surface materials by area.
How do I calculate the square footage of a house?
Measure each finished, heated room (or the exterior footprint of each floor) and add the areas. In the United States, residential square footage for listings and appraisals is commonly measured following ANSI Z765, which uses exterior dimensions of finished, above-grade space and excludes garages and unfinished basements. A room-by-room interior total will usually come out a little lower than a listed figure because it leaves out wall thickness.
How many square feet are in an acre?
An acre is exactly 43,560 square feet, which is 4,840 square yards or about 4,047 m². A quarter-acre lot is 10,890 sq ft. For a lot, enter its sides as a rectangle or trapezoid; for an irregular lot, divide it into triangles.
How do I find the area of an irregular shape?
Break it into shapes you can measure: rectangles for the main body, triangles for angled corners, trapezoids for splayed walls, and circles or half circles for curves. Add the pieces and subtract any cut-outs. The more pieces you use, the closer the total gets to the true area.
Should I measure to the inside or outside of the walls?
For materials that go inside a room — flooring, rugs, paint for the floor — measure inside, wall to wall at floor level. Exterior dimensions are used for a building's footprint, foundations, and some property records. Mixing the two in one total is a common source of small but real discrepancies.
How do I estimate cost from square footage?
Multiply the area by the price per unit in the same unit: 324 sq ft at $4.50 per sq ft is $1,458. Make sure the quote's unit matches your area — a price per square yard is 9 times a price per square foot, so $36/sq yd equals $4/sq ft. Open the cost estimate option above to do this automatically; it doesn't add any waste allowance.
Is "10 square feet" the same as "10 feet square"?
No. "10 square feet" is an amount of area, in any shape — a 2 ft × 5 ft strip qualifies. "10 feet square" describes a square whose sides are each 10 ft, which is 100 square feet. The phrasing shows up in older plans and listings, so check which one is meant before converting.
How accurate do my measurements need to be?
The nearest inch (or centimetre) is enough for almost any home project. The error grows with the size of the space: being 1 inch short on both sides of a 12 × 12 ft room changes the area by about 2 sq ft, roughly 1.4%. On a large, open area, errors of that size add up across several rooms, which is why each room should be measured separately rather than estimated from the house's outside dimensions.
Does a vaulted or sloped ceiling change a room's square footage?
Not the floor area. Square footage of a room is measured on the floor, so a 12 × 14 ft room is 168 sq ft whether its ceiling is 8 ft flat or vaulted to 14 ft. Ceiling height matters for volume (heating and cooling) and for wall and ceiling surface area, which is a different measurement from the one this calculator makes.
Do I include closets and the area under cabinets?
Include closets if the same surface continues into them — measure the closet as its own rectangle and add it. Leave out the footprint of fixed cabinets or a kitchen island if nothing will be installed underneath; enter it as a subtracted area. Check the relevant material calculator for how it treats these areas, since some finishes run under appliances.
Related tools
Flooring Calculatorturn this floor area into boxes of laminate, hardwood, or vinyl plank, with a waste allowance for your layout.Tile Calculatorconvert the area into a tile and box count for your tile size and grout joint.Carpet Calculatorcarpet is ordered off fixed roll widths, so seams change the yardage — get the square yards to actually buy.Measuring walls instead of a floor? The paint and drywall calculators take wall dimensions directly and subtract doors and windows for you.