Square footage
calculator.

How to calculate square footage

For a rectangular room, measure the length and width in feet and multiply them. The result is an area, written in square feet or sq ft. A 12-foot by 10-foot room is 120 square feet. If your tape measure shows inches, convert those inches to feet before multiplying. Six inches is 6 ÷ 12, or 0.5 feet, so a room measuring 12 ft 6 in by 10 ft is 12.5 × 10 = 125 sq ft.

Choose the shape that matches your space

A rectangle uses length × width. A square uses side × side. A triangle needs a base and its perpendicular height; the height meets the base at a right angle. A circle can use its diameter, with area π × diameter² ÷ 4. A trapezoid uses its two parallel sides and the perpendicular distance between them. For an L-shaped room, measure the large outside rectangle and subtract the missing rectangular corner, or divide the floor into two non-overlapping rectangles.

For oval or sloped-sided shapes, the calculator labels the needed dimensions explicitly. An ellipse uses its major and minor diameters; a parallelogram uses the base and perpendicular height, not the sloping side. If a room is more complicated, draw a quick sketch and split it into simpler sections. Add covered sections and subtract only areas that will not receive the material.

Measure a room without counting area twice

Measure at floor level and keep the tape straight. Record each dimension immediately, including whether it is feet, inches, meters or decimal feet. Measure the full length and width of a simple room. If the walls are not parallel or the room is not square, take extra measurements and break the outline into smaller rectangles or triangles. A single pair of dimensions can hide a bay, alcove or angled wall.

Measure closets separately when the same flooring continues into them. Decide whether a permanent cabinet or built-in is included based on where the new floor will actually go. Do not subtract an area that is covered by the flooring, and do not add a closet if it is already inside the main rectangle. For multiple rooms, calculate each room and add the room totals.

Use consistent units

Area units are squared. One square yard equals 9 square feet; one square foot equals 144 square inches and 0.09290304 square meters. Convert dimensions before multiplying, or convert the finished area using the correct area factor. Do not multiply a length conversion by itself unless you are converting both dimensions. For example, 10 ft × 10 ft is 100 sq ft, which is about 9.29 sq m.

Feet-and-inches measurements are a common source of mistakes. A length of 10 ft 6 in is 10.5 ft, not 10.6 ft. Convert the inch portion by dividing by 12. If you use decimal feet, enter the decimal value directly. Keep the unit selector consistent for every section in a room.

What the result does and does not mean

The result is the geometric area from the measurements entered. It is not automatically the amount of flooring, tile, paint or other material to buy. Material estimates may require a cutting allowance, product-specific coverage, a whole-package round-up or installation details such as a tile pattern. A room area can also differ from an official real-estate measurement, which may follow separate standards and include or exclude areas differently.

For a flooring order, start with the measured area, group spaces that use the same product, apply an allowance that matches the product and layout, and round up to whole boxes. Keep box coverage visible in your notes. Compare your measurements against the package label and ask the supplier or installer to check unusual layouts before purchase. See the flooring box calculator and the guide to flooring allowance and box rounding.

Quick checks before you use the number

• Both dimensions use the same unit, and the answer is labeled as square feet.
• Inches were converted by dividing by 12; feet and inches were not treated as decimal digits.
• The selected shape matches the measurements you took, especially height, diameter and radius.
• Sections meet without overlap, and subtracted cutouts fit inside the measured outline.
• The final material order accounts for product coverage and whole-box packaging separately from area.

If you want to save your notes, use one room name per space and share or print the result for a second check. The calculator keeps saved inputs in your browser on this device. Start with a simple rectangle above, then add rooms or sections if the actual floor plan needs them.

Keep a multi-room project organized

Give each room a short name and record its dimensions before adding it to a project. If a hall connects two rooms, decide whether you are treating it as its own section or including it inside one room outline, then count it once. This makes the total easier to compare with a supplier quote and helps you spot a value entered in the wrong unit.

Your editable measurements are saved in this browser on this device. You can return to the project later or share a link when you want someone else to review the values. The calculation remains an estimate based on the dimensions entered, so keep your sketch or worksheet for important purchases.

Want to record measurements on paper? Get the worksheet before you visit the space.