Room size
Leave both at 0 if you are hanging around the openings or have not counted them yet.
Waste
10% is a typical hang. 15% if the room jogs or you are new to cutting. 5% is tight.
Buy
- Net sq ft
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- With waste
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- 4×8 sheets
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- 4×12 sheets
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- Joint compound
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- Tape (250 ft)
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Enter length, width, and height.
This is an estimate, not a contractor quote, not a materials takeoff, and not install advice. Mixed compound units (gallons and 4.5-gal tubs) are a known nit — not a compound calculator. It does not choose a hang direction, fire rating, or moisture board. Confirm sheet size, compound, and tape at the store.
How the sheets are counted
This is a 4×8 sheet count, not a contractor quote. Wall area is the room’s perimeter times height: 2 × (length + width) × height. Each door knocks off 20 square feet (a typical 3 ft × 6 ft 8 in interior door). Each window knocks off 15 square feet. Leave both at zero to skip openings. The ceiling, if you turn it on, is length × width. Openings cannot take the walls below zero.
Waste is applied to that net square footage (default 10%). A 4×8 sheet is 32 square feet; a 4×12 is 48. Sheet counts round up so a leftover still becomes another board. Joint compound is 1 gallon per 100 square feet, shown as 4.5-gallon tubs. Tape is 370 feet per 1,000 square feet, shown as 250-foot rolls.
wall_sq_ft = 2 × (L + W) × H net = max(0, wall_sq_ft − doors×20 − windows×15) + (ceiling ? L×W : 0) with_waste = net × (1 + waste) sheets_4x8 = ceil(with_waste / 32) sheets_4x12 = ceil(with_waste / 48) compound_gal = ceil(with_waste / 100) buckets = ceil(with_waste / 100 / 4.5) tape_ft = with_waste × 0.37 tape_rolls = ceil(tape_ft / 250)
Example: 12 ft × 10 ft × 8 ft, 0 openings, 10% waste, walls only. Walls 352 × 1.10 = 387.2 sq ft. 387.2 ÷ 32 = 12.1 → 13 sheets of 4×8 (or 9 sheets of 4×12). About 4 gallons of joint compound (one 4.5-gal tub) and one 250-ft roll of tape.
FAQ
Why 4×8 sheets, not square feet?
You buy boards, not 387 square feet off a roll. A 4×8 sheet is 32 square feet. A leftover still becomes another sheet, so the count rounds up. Square footage is the intermediate, not the order.
How many 4×8 sheets for a 12×10×8 room at 10% waste?
Walls = 2 × (12 + 10) × 8 = 352 sq ft. 10% waste → 387.2. 387.2 ÷ 32 = 12.1 → 13 sheets of 4×8 (or 9 of 4×12). That is the documented fixture. Openings, the ceiling, and a different waste chip change it. Not a contractor quote.
4×8 or 4×12 — does this page pick?
No. It shows both counts. 4×8 is easier to carry. 4×12 can skip a joint on an 8-foot wall. Pickup, stairs, and hang direction decide the size — not this calculator.
Why mixed compound units — is this a compound calculator?
No. Mixed compound units are a known nit: gallons (1 gal per 100 sq ft) and 4.5-gallon tubs on the same card, plus tape as 250-ft rolls. That is a rough cart check, not a finishing spec, and not a compound calculator. This page does not invent one.
Do doors, windows, and the ceiling change the 13 sheets?
Yes. Leave openings at 0 to hang around them. Each door knocks off 20 sq ft; each window 15. The ceiling is optional (length × width) and is off by default. Openings cannot take the walls below zero.
Is this a contractor quote?
No. Quantity math only: walls, openings, waste, round up to 4×8 sheets. Not a contractor quote. Not a materials takeoff. Not hang advice. Not a fire-code check. Not a compound calculator. Confirm with the store and whoever hangs the board.