Calculate square footage for one room or a whole project using feet and inches, decimal measurements, or metric units. Add L-shaped spaces and multiple areas, then separate the measured total from the amount you may need to order.
Reviewed and updated July 10, 2026
Use it when you want to know
Measure in feet and inchesEnter tape-measure readings directly without turning inches into decimal feet.
Add every room or project areaLabel spaces, include or exclude them, and see a running total with a clear breakdown.
Plan beyond the raw measurementOptionally add a project allowance while keeping the exact measured area visible.
Calculator
Measure one area or total a whole project
Start with one rectangle, then add rooms, closets, walls, patios, or lawn sections. Results update as you type, and the raw measurement always stays separate from the optional allowance.
Guide
How do you calculate square footage for a home project?
Square footage measures a flat surface. The reliable workflow is to measure each usable section, calculate it separately, and only then add the areas that belong in the project.
Start with the surface that will receive material
For a rectangular floor, patio, wall, or lawn section, multiply length by width. Both measurements must represent the same unit before multiplication. A 12-foot by 10-foot room is 120 square feet.
Measure at the surface you are covering. Flooring measurements belong at floor level; wall projects use wall width and height. The Home Depot also recommends dividing odd spaces into smaller sections, measuring each section, and adding the results.
Rectangle formulaSquare footage = length in feet × width in feet
Keep full precision while calculating. Round only the final total or the quantity you must purchase.
How do feet and inches become square feet?
Twelve inches equal one foot, so divide inches by 12 before adding them to whole feet. Six inches is 0.5 foot—not 0.6 foot. A room measuring 10 feet 6 inches by 8 feet 3 inches becomes 10.5 × 8.25, or 86.625 square feet.
How do you measure an L-shaped room?
One method is to measure the largest outer rectangle and subtract the missing corner. For a 15-by-12-foot outline with a 5-by-4-foot cutout, the area is 180 − 20 = 160 square feet. Alternatively, split the L into two non-overlapping rectangles and add them.
How do you total multiple rooms?
Calculate each room first, then add the finished areas. A 120-square-foot bedroom plus a 35-square-foot closet totals 155 square feet. Adding both lengths and both widths before multiplying creates empty space that is not part of either room.
What should you include or exclude?
Follow the material path. Include closets and alcoves when the same flooring continues into them. Subtract an island only if the new surface will not run underneath it. For walls, large openings may be deducted, but paint and drywall estimators may use different allowances.
Measured area and purchase area are different
Carpet is cut from fixed-width rolls, and flooring or tile comes in cartons. A strange room may need more material than its exact area suggests. Use the raw total as the starting point, then follow the product coverage and layout instructions.
A project allowance is not a universal rule
Many simple projects start around 5% to 10% extra, but patterns, diagonal layouts, breakage, defects, and fixed package sizes can require more. The calculator leaves the allowance off until you choose it.
Project totals are not appraisal measurements
Professional property reporting can use exterior dimensions, ceiling-height rules, above-grade and below-grade classifications, and standards such as ANSI Z765. Do not use this interior project estimate for a listing, appraisal, permit, lease dispute, or legal record.
A 12-foot by 12-foot room is 144 square feet because 12 multiplied by 12 equals 144. Measure wall to wall at floor level when you are planning flooring.
How do I calculate square footage with feet and inches?
Convert the inches in each measurement to a fraction of a foot, then multiply length by width. For example, 10 feet 6 inches is 10.5 feet. This calculator performs that conversion automatically.
How do I total the square footage of multiple rooms?
Calculate each room separately, then add the room areas together. Do not add all lengths and widths first, because that creates an imaginary larger rectangle and overstates the area.
How do I calculate the square footage of an L-shaped room?
Measure the full outer rectangle and subtract the rectangular missing corner. You can also split the L-shape into two non-overlapping rectangles and add their areas.
Should I include closets, islands, doors, or windows?
Include every surface that will receive the material. Include a closet if flooring continues into it. For a wall project, subtract large doors or windows only when the product instructions or your estimating method calls for it. Do not subtract a kitchen island from flooring if flooring will run underneath it.
How many square feet are in a square yard or square meter?
One square yard equals 9 square feet. One square foot equals 0.09290304 square meters. The result card shows both conversions automatically.
How much extra material should I add?
The right allowance depends on the material, layout, package size, and manufacturer instructions. Five to ten percent is a common starting range for many simple projects, while patterns, diagonal layouts, fragile materials, or complicated cuts may require more.
Can this calculate official home or apartment square footage?
No. This calculator is for home-project estimates based on the surfaces you measure. Appraisals, listings, permits, leases, and legal property records may use exterior measurements and professional standards that differ from a room-by-room interior total.