Square Footage Calculator - Rooms, L-Shapes, Circles

How to measure square footage

Square footage is just area: how many 1 × 1 ft squares fit on a floor, a wall, or a patch of lawn. For a rectangle, measure the length and the width in feet and multiply. A 12 × 14 ft bedroom is 168 sq ft. That is the whole trick, and every other shape is a variation on it.

Measure wall to wall at floor level and write the numbers down as you go. Convert inches to decimal feet by dividing by 12: 6 inches is 0.5 ft, 3 inches is 0.25 ft, 9 inches is 0.75 ft. So a room that is 11 ft 6 in by 13 ft 3 in becomes 11.5 × 13.25 = 152.4 sq ft.

Irregular rooms: split them up

Real rooms are rarely perfect rectangles. The fix is to split the space into shapes you can measure, work out each one, and add them. That is why the calculator lets you add as many areas as you want and mix shapes.

An L-shaped room is two rectangles. Draw a line where the L turns, measure each part, and add them. A 10 × 8 ft main area plus a 6 × 4 ft nook is 80 + 24 = 104 sq ft. For a round feature like a bay or a circular patio, measure the diameter and use π × (d ÷ 2)². A 10 ft circle is 78.5 sq ft. For a triangular corner or an angled garden bed, measure all three sides and the calculator uses Heron's formula, so you never need to find the height. Three 10 ft sides give 43.3 sq ft.

Closets, hallways, and alcoves are separate rectangles. Add them if the flooring or paint continues into them; leave them out if it does not.

Worked example: flooring a bedroom and an L-shaped office

Say you are putting the same plank floor in a 12 × 14 ft bedroom and an L-shaped office made of a 10 × 8 section and a 6 × 4 section. The bedroom is 168 sq ft and the office is 104, for 272 sq ft total. That is 30.2 square yards or 25.3 square meters.

At $4.50 per sq ft installed, the job costs $1,224 before waste. Flooring and tile should always include extra for cuts, so set waste to 10% and the order quantity becomes 299.2 sq ft, and the cost about $1,346. Diagonal or herringbone layouts need 15 to 20%.

Square feet, square yards, and acres

Carpet is often priced per square yard: divide square feet by 9. Sod, seed, and fertilizer are sold by square feet per bag or per pallet, and land is sold by the acre, which is 43,560 sq ft. One square meter is 10.764 sq ft, so if a European tile box says 1.44 m², it covers 15.5 sq ft. Toggle the calculator to metric if your tape measure or plans are in meters and it will show both.

Common mistakes

Multiplying feet by inches. 12 ft by 30 in is not 360 sq ft. Convert first: 30 in is 2.5 ft, so it is 30 sq ft.

Using the listing's square footage for materials. A home's advertised square footage follows appraisal rules, usually measured from outside walls, and includes spaces you will not floor or paint. Measure the actual rooms.

Forgetting waste. Area is the floor you cover; the material you buy is always more because of cuts, pattern matching, and the occasional broken piece.

Measuring only one wall on a room that is out of square. Older homes can be off by several inches. Measure both long walls and use the larger number.

When to get a professional measurement

For a single room of flooring, your own tape measure is accurate enough. For appraisals, property taxes, or a home sale, square footage follows specific standards (ANSI Z765 in the U.S.) and should be measured by an appraiser. For large landscaping or roofing projects, satellite measurement services or a contractor's walk-through catch slopes and odd angles that a quick tape measurement misses. Many flooring stores also measure for free before they quote an installation.