How to Calculate Square Feet of a Wall

Measure wall area in three steps

Use a tape measure and a simple sketch. Name the wall, such as “kitchen north wall,” before recording its dimensions.

1. Measure the wall.Record its full width and height. Use the two end heights if the top slopes.
2. Record the parts to leave out.Measure each excluded door, window or other area. Keep it under the wall it belongs to.
3. Check the net area.Start with the wall area, add any extra sections, and subtract the excluded sections once.

One wall needs width and height. A room’s floor length and width measure a different surface. For floors, use the room measurement guide.

Measure wall width and height

Use feet and inches or metric units

For a width of 12 ft 6 in, enter 12 in the ft box and 6 in the in box. For inches only, leave ft blank. Fractional inches such as 6 1/2 are also accepted.

Select Feet (ft) for decimal feet such as 12.5. In ft + in mode, leave in blank or 0 when using decimal feet. You can also enter m, cm or mm; metric area is shown in m².

When calculating by hand, use the same length unit for width and height. Feet × feet gives square feet; meters × meters gives square meters.

Subtract door and window areas

First decide which surfaces your measurement excludes. Measure the width and height of each excluded area, using the same boundary on your sketch and in your calculation. Glass size alone may not describe the whole area you are leaving out.

In the wall calculator, use Subtract section → Window, Door or Other section. Give each section a name if that helps you identify it.

Several openings of the same size

Enter one opening’s dimensions, then use Quantity only for matching sizes. Two windows measuring 3 ft × 4 ft each remove 2 × 12 = 24 sq ft. Different sizes need separate sections.

Count each opening once. Do not subtract the same space again as “other area.” A section belongs to one wall, so an opening on the kitchen wall does not reduce the living room wall.

For another surface you will cover, such as the side of a deep recess, measure that surface separately and use Add section. Avoid counting a surface that is already included.

Example: calculate net wall square footage

This example excludes the rectangular window and door areas shown above. Your own excluded surfaces may be different.

Measure a wall with a sloped or pointed top

One straight sloping top

Choose Wall with a sloped top. Measure width A horizontally, left height B vertically and right height D vertically. Both ends must be vertical, and the top between them must be straight.

Record the actual end heights; the calculator averages them. Subtract any excluded openings from this area afterward.

A pointed top or several changes in height

For a rectangular wall with a triangular top, use Rectangular wall for the lower rectangle, then Add section and choose Triangle. Measure the triangle’s height from the top of the rectangle to the peak, not from the floor. Its base and height must meet at a right angle.

For example, a 10 ft × 8 ft rectangle plus a triangle with a 10 ft base and a 3 ft height gives 80 + 15 = 95 sq ft. The triangle must not include the rectangle again. Split more complex outlines into suitable non-overlapping parts.

Calculate the square footage of several walls

Use Add another wall for each separate wall. Record its width, height and its own openings. Name the walls by room and position, such as “kitchen north wall” and “kitchen east wall.”

The example wall above has 63 sq ft after openings. A second wall measuring 10 ft × 8 ft with no deductions adds 80 sq ft, for a combined 143 sq ft.

If all the walls have the same height

You can check the total before openings by adding all wall widths and multiplying by the common height. For a rectangular 12 ft × 10 ft room with 8 ft walls: (12 + 10 + 12 + 10) × 8 = 352 sq ft. In the tool, still record each wall separately to keep its openings in the right place.

Floor area alone is not wall area. The 12 ft × 10 ft floor is 120 sq ft; the four walls above total 352 sq ft before openings. The ceiling is another surface and is not included in that wall total.

Before you use wall area to buy materials

Net wall area describes the flat surfaces included in your measurement. The quantity you buy also depends on the product and how it is installed.

Area or box coverage

In the wall calculator, select the measured walls using the same product, then enter waste, box coverage and a price if needed. Read coverage from the product label.

Paint

Paint quantity also depends on the number of coats, product coverage and application conditions. This guide does not convert wall area into gallons.

Wallpaper and sheet materials

Full strips, pattern matching and cutting can affect the order. Follow the product’s measuring and ordering instructions; net area alone is not a roll count or cutting layout.

Keep your measured dimensions separate from any waste allowance. Do not increase wall width or height just to add spare material.