Drywall Calculator
Drywall comes in 4-foot-wide sheets — 8, 10, or 12 feet long. Enter your total wall area and get the sheet count with waste, rounded up.
Drywall Calculator
About this drywall calculator
Drywall estimating starts with one number: total square footage of the walls and ceilings you are covering. Measure each wall (length × height), add them up, and subtract nothing — doors and windows are left in the total because the waste allowance covers the cut-outs, and it is better to have a spare sheet than to run short mid-job.
Sheet choice matters. 4×8 sheets are the easiest to handle solo and fit through any doorway. 4×12 sheets cover long walls with fewer seams (fewer seams = less taping and mudding), but they are unwieldy and need two people plus clear stairwell access. This calculator works with all three standard sizes.
Beyond sheets, budget joint compound (roughly one 5-gallon bucket per 300–400 sq ft for a first-timer), tape, screws (about 1 lb per 100 sq ft), and corner bead — the calculator covers sheets; the rest scales with the same square footage.
Worked example: drywall for a 12×12 room
Take a 12×12 ft room with 8-ft ceilings. Walls: 4 walls × 12 ft × 8 ft = 384 sq ft. Ceiling: 12 × 12 = 144 sq ft. Total: 528 sq ft. Subtract roughly 36 sq ft for a door and a window: 492 sq ft. Add 10% waste for cuts: 492 × 1.1 = 541.2 sq ft. With 4×8 sheets (32 sq ft each): 541.2 ÷ 32 = 16.9, rounded up to 17 sheets.
Seventeen sheets is a comfortable one-room order — and it shows why the waste allowance matters: without it you would buy 16 sheets and discover mid-project that the closet wall needs one more. Drywall is cheap; a second delivery trip is not.
Buying tips
Longer sheets mean fewer seams: 4×12 sheets on long walls and ceilings cut your taping work substantially and give flatter walls. The tradeoff is handling — a 4×12 sheet is a two-person carry and needs a truck or delivery, while 4×8 sheets fit in many SUVs. For ceilings, consider 5/8-inch board: it resists sagging between joists better than 1/2-inch.
Do not forget the finishing materials. A 5-gallon bucket of joint compound covers roughly 400–500 sq ft for taping plus three coats — our 12×12 example (~541 sq ft) needs about 2 buckets. Add a roll of paper tape (about 500 ft per room is plenty), and buy one extra bucket: running out mid-finish is miserable.
How to use
- Measure each wall's length × height in feet and add them together (include ceilings if covering them).
- Enter the total in square feet.
- Pick your sheet size and a waste allowance.
- Press Calculate for the sheet count, rounded up.
Good to know
- Covers sheets only — not mud, tape, screws, or corner bead.
- Assumes rectangular walls; heavily angled or curved walls need manual layout.
- Moisture-prone areas (bathrooms, basements) need mold-resistant board — same math, different product.
- Hang long sheets horizontally on walls when you can — fewer butt joints means less taping and a flatter finish. You will want a helper and a drywall lift for ceilings.
- Budget joint compound separately: roughly one 5-gallon bucket per 400–500 sq ft for tape plus three coats. Paper tape, not mesh, for the strongest joints.
Frequently asked questions
How many drywall sheets do I need for a 12x12 room?
A 12×12 room with 8 ft ceilings has about 384 sq ft of wall (four 12×8 walls) plus 144 sq ft of ceiling = 528 sq ft. That is 19 sheets of 4×8 with 10% waste. Measure your actual ceiling height and add any closets.
What size drywall sheets should I buy?
4×8 for easy handling and tight spaces, 4×12 for long walls where fewer seams save taping time. 1/2-inch thick is standard for walls; 5/8-inch for ceilings and fire-rated assemblies.
How do you calculate drywall?
Total wall and ceiling square footage ÷ sheet square footage, plus 10% waste, rounded up to whole sheets.
How much does it cost to drywall a room?
Sheets run roughly $12–$20 each depending on size and type; mud, tape, and fasteners add roughly 30–40% on top for DIY. Labor typically doubles or triples the materials cost.
Should I subtract doors and windows from drywall area?
No — leave them in. The cut-outs generate the waste the allowance accounts for, and running short is worse than having one spare sheet.
How many drywall sheets do I need for a 12x12 room?
Walls (4 × 12 × 8 ft) = 384 sq ft plus a 144 sq ft ceiling = 528. Leave the door and window in (the waste allowance covers the cut-outs), plus 10% waste ≈ 581 — which works out to 19 sheets of 4×8. Enter your exact area above for your room.
Should I use 4x8 or 4x12 drywall sheets?
4×12 sheets mean fewer seams on long walls and ceilings — less taping, flatter walls. But they are heavy (a two-person job) and need a truck or delivery; 4×8 sheets fit in most SUVs and are easier to handle solo.
How much joint compound do I need?
Roughly one 5-gallon bucket per 400–500 sq ft of drywall for taping plus three finish coats. A 12×12 room (about 540 sq ft of drywall) needs roughly 2 buckets — buy one extra, because running out mid-finish stalls the whole job.
Do I measure the ceiling separately from the walls?
You can simply add ceiling square footage to the wall total and let the waste allowance cover the extra cuts. If the ceiling uses different board — for example 5/8-inch to resist sagging — calculate it as a separate run so you order the right thickness.