Drywall calculator

Enter the room and this returns the number of sheets to buy, with screws and tape alongside. The arithmetic is geometry rather than a trade secret, so it is printed below and works on paper — and the one quantity nobody can calculate for you is named rather than guessed.

Nothing you type here is sent anywhere. The arithmetic runs on your device and the page makes no network request — see the privacy note. None of this is a quote; see the terms of use.

The formula

Wall area is the room perimeter multiplied by the wall height: two times length plus width, times height. Ceiling area is length times width. Add them, divide by the area of one sheet, add the waste allowance, round up.

A 12-by-12-foot room with 8-foot ceilings: the perimeter is 48 feet, so the walls are 384 square feet, and the ceiling adds 144. That is 528 square feet, or 16.5 sheets of 4-by-8 before waste and 19 after ten percent.

Longer sheets are not simply better value. They mean fewer butt joints, which is the finisher's argument for them, and they are heavier and harder to carry up a stairwell, which is the homeowner's argument against. The square footage is identical either way.

Why openings are not subtracted

This calculator counts doors and windows as covered surface, and that is deliberate rather than lazy. Board gets cut around an opening and the offcuts are rarely the right size for anywhere else, so the material a door removes is close to the material the cutting wastes.

Deduct only when an opening is genuinely large — a double patio door, a wall that is mostly glazing — and even then deduct half of it. Ordering short on drywall is a second trip rather than a saving, since a sheet costs a few dollars and a wasted afternoon costs more.

The quantity this page will not invent

Joint compound. Most drywall calculators print a number here, and the number is guesswork dressed as arithmetic: coverage depends on the product, how many coats go on, whether it is applied by hand or with a box, and what level of finish the job is aiming for. Every bag and bucket prints its own coverage chart, and that chart is the authority.

Tape is different, because tape is geometry. This page estimates it as eight linear feet per 4-by-8 sheet for the long seams plus the room perimeter for inside corners, which is a working assumption printed here rather than a published figure — a sheet hung vertically or a room with butt joints staggered differently will shift it.

Screws are arithmetic too: about 32 per 4-by-8 sheet, which is one every 12 inches along four stud lines at 16 inches on center. A 1-pound box holds roughly 180 of the 1-1/4 inch screws used on half-inch board, so it covers about five or six sheets.

What it costs once hung

Quantities are only half the question. HomeAdvisor puts drywall installation at a national average of $2,103 with a typical range of $1,000 to $3,254, or $1.50 to $3.50 per square foot installed, read September 16, 2026 — and the striking part of the split is that finishing costs more than hanging. The breakdown by board type, by room and by stage is in what drywall installation costs.

If the drywall is one line in a larger job, the remodel cost calculator gives the room-level range, and interior painting costs covers what happens to the wall after the compound is sanded.