Drywall calculator
Sheets, joint compound, tape and screws for a room — with 4×8 and 4×12 compared side by side.
Calculator
Detailed breakdown
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How to use this calculator
Measure
Measure the room's length, width and wall height in feet, and decide whether you are hanging the ceiling too.
Calculate
Once you hit calculate, results update as you type. Change any number to compare options instantly.
Order
Print the estimate and take it to your supplier. Quantities are rounded up so you don't come up short.
Sheet counts, and why 4×12 is not always the answer
Drywall math starts with surface area. Walls are the room perimeter times height; add the floor area if you are hanging the ceiling too. A 12 by 15 foot room with 8 foot walls gives 432 square feet of wall plus 180 of ceiling — 612 square feet total.
Divide by sheet size to get the count. A 4 by 8 sheet covers 32 square feet, so that room takes 20 sheets. Move to 4 by 12 sheets at 48 square feet each and you need only 13 — with meaningfully fewer seams to tape, which is the real advantage.
The catch is handling. A 4 by 12 sheet of half-inch drywall weighs roughly 55 lb for lightweight board and up to about 77 lb for standard, and is genuinely awkward for one person, especially overhead. If you are working alone, the extra seams from 4 by 8 sheets are usually the better trade-off.
For finishing materials, plan on roughly one bucket of joint compound per 450 square feet for a three-coat finish, about 0.4 linear feet of tape per square foot, and just over one screw per square foot. Buy an extra sheet beyond the calculated count — you'll destroy at least one on a cut, and matching thickness later is more annoying than it sounds.
Frequently asked questions
How many sheets of drywall for a 12x15 room?
About 20 sheets of 4x8, or 13 sheets of 4x12, including the ceiling. Add one extra for cuts and mistakes.
Should I use 4x8 or 4x12 sheets?
4x12 means fewer seams and a faster finish, but each sheet runs 55 to 77 lb depending on whether it is lightweight or standard board. Working alone, 4x8 is far more manageable.
How much joint compound do I need?
Roughly one 5-gallon bucket per 450 square feet for a standard three-coat finish. Level 5 finishes use more.
How many screws per sheet?
About 35 screws per 4x8 sheet — every 12 inches on studs, every 8 on ceilings. That is a little over one screw per square foot.
What thickness should I use?
Half inch for most walls, five-eighths for ceilings and where a fire rating requires it. Check local code, especially for garages and shared walls.
Sources
Formulas and material assumptions on this page follow published industry guidance: