Door and window sizes for paint and drywall estimates

Doors

Most doors you will measure in a house are 80 in (6 ft 8 in) tall, in widths from 24 to 36 in. Older houses and custom work vary, so measure: width across the slab and height from the floor. For paint, the door’s area is what comes off the wall; for painting the door itself you need both faces.

The 36 × 80 in door is exactly 20 sq ft, which is why calculators take 20 sq ft off the wall for each door. Exterior doors are commonly 36 in wide and thicker (1¾ in against 1⅜ in for interior doors). Painting the door itself is a quart job: how much paint for a door and how much paint for a front door. From spray cans it is seven or eight: how many cans of spray paint to paint a door.

Garage doors

Single garage doors are often 8 or 9 ft wide and 7 ft tall (56–63 sq ft); double doors 16 ft wide and 7 ft tall (112 sq ft). That is a big chunk to take off when estimating the walls of a garage for drywall or paint: how many sheets of drywall for a 2 car garage and how much paint for a garage door.

Windows

Window makers describe sizes with a four-digit code. Pella explains it this way: the first two digits are the width in feet and inches, the last two the height, so a 2840 is 2 ft 8 in wide and 4 ft 0 in tall. The code can describe the window or the rough opening, so check which. These are some of the common sizes Pella lists:

With its casing, a typical bedroom window is about 3 × 5 ft, which is where the usual 15 sq ft allowance comes from. Picture windows and patio doors are much bigger; measure them.

How to use the sizes in each estimate

• Paint: subtract doors and windows from the wall area. The room paint calculator does it at 20 and 15 sq ft each; change the sizes under More options. How much paint for a 12x12 room shows the effect: 50 sq ft off 384.
• Drywall: USG’s guide says to subtract large openings such as doorways and picture windows, but not small openings. Ordinary windows are usually cut out of full sheets, so they don’t reduce the sheet count much.
• Wallpaper: count strips, not area. Each door or window saves about one or two strips; the short pieces above and below come from roll offcuts. See how many rolls of wallpaper for a 12x12 room.
• Trim, tape and caulk: these follow the edges of openings. A door casing is about 18 ft of edge, a 3 × 5 ft window’s about 19; see how many rolls of painter’s tape for a 12x12 room and how many tubes of caulk per window.

Measuring tips

• Measure each opening to the outside edge of its trim when subtracting from paint, since the trim isn’t painted with the wall color.
• Write sizes as width × height, and keep inches for doors and windows; it avoids mixing up 2 ft 8 in with 2.8 ft.
• Don’t subtract anything smaller than about 10 sq ft: outlets, vents and small mirrors don’t change the gallons.
• If a wall is mostly window, measure the wall pieces that are left instead of subtracting.