How many square feet is it?

Square footage is the number every material starts from

Almost every material estimate begins with area. Multiply the length by the width, both in feet, and you have square feet: a 12 by 10 ft bedroom is 120 ft². Measure wall to wall at floor level, and round each measurement up to the next inch rather than down — a short measurement is how people end up one box of flooring short.

Rooms that are not rectangles are just rectangles stuck together. An L-shaped living room might be a 20 by 12 ft main area plus a 10 by 8 ft dining nook: 240 + 80 = 320 ft². Enter each piece as its own area above. For a closet or bump-out, add it as a third area. For a notch cut out of a room, such as a kitchen island you will not tile under, work out the notch and subtract it yourself.

Once you have the area, the unit depends on what you are buying. Tile, laminate, paint and drywall are sold by the square foot. Carpet and sod are often quoted by the square yard, which is square feet divided by 9. Land and large lawns are sometimes described in acres: one acre is 43,560 ft².

Area alone is not an order quantity. Every material needs a waste allowance for cuts, typically 5–10% for flooring and 10–15% for diagonal tile. Take the square footage from here into the matching calculator — flooring, tile, carpet, paint or sod — and it will add the waste and round up to whole boxes, rolls or gallons.

Shapes that are not rectangles

Most rooms break into rectangles, but some spaces do not. These formulas cover almost everything else. Measure in feet and the result is in square feet.

Work out the odd shape separately and add it to the rectangles. For a room with an angled wall, split it into a rectangle and a triangle.

A worked example: a whole floor for new flooring

An open-plan floor might be a 22 × 14 living area, a 12 × 10 kitchen and a 3 × 12 hallway: 308 + 120 + 36 = 464 ft², or 51.6 square yards. If you are not putting flooring under the kitchen cabinets, measure the cabinet footprint (for example 10 × 2 feet) and subtract it: 444 ft². Then take that figure to the flooring calculator, which adds the waste and rounds to whole boxes.

Unit conversions

Measuring tips that save a second trip

• Measure twice, at two heights. Walls are rarely perfectly parallel. Measure a room at both ends and use the larger number.
• Use a laser measure for long rooms. A tape that sags over 20 feet reads long; a laser does not.
• Sketch before you measure. Draw the floor, split it into rectangles, and write each measurement on the sketch. It is the easiest way to catch a forgotten closet.
• Round up to the next inch. A small overestimate costs a few dollars; a short one costs a trip back to the store.