Everyday
Drywall Calculator
Figure out how many drywall sheets a multi-room project needs, with door and window openings deducted.
How it works
Behind the numbers
Drywall math starts with wall area: for each room, twice the length-plus-width times the ceiling height, plus the ceiling itself when you check that box. Door and window openings come off next — a standard 3×7 ft door counts as 21 sq ft and a 3×5 ft window as 15 sq ft — because you hang no board where the opening is.
Sheets round up per room rather than across the whole project, since offcuts rarely transfer cleanly between rooms. The sheet size you pick changes the count: a 4×12 ft sheet covers 48 sq ft against 32 for a 4×8, so bigger sheets mean fewer seams to tape, at the cost of needing two people to hang them.
The consumables are rule-of-thumb estimates, not quotes. Joint compound runs about a gallon per 100 sq ft, so a 4.5-gallon bucket covers roughly 450 sq ft; screws run about one per square foot (around 28 per 4×8 sheet); tape is estimated at 10 linear feet per sheet on 250-ft rolls. Waste allowance defaults to 10%; use 15% for rooms with angled walls or closets.
FAQ
Questions, answered
How many drywall sheets do I need for a 12x12 room?
Take a 12×12 ft room with 8-ft ceilings: walls are 384 sq ft and the ceiling adds 144, for 528. Subtract one door (21) and one window (15) to get 492 sq ft. With 4×8 sheets (32 sq ft) and 10% waste: 492 × 1.1 ÷ 32 = 16.9, so 17 sheets.
Should I use 4x8 or 4x12 drywall sheets?
4×12 sheets cover 50% more area per sheet, which means fewer seams to tape and finish — the slowest part of drywalling. The tradeoff is handling: 12-ft sheets are heavy, need two people, and do not fit in tight stairwells or small elevators.
How much joint compound do I need?
Plan on about one gallon per 100 square feet of drywall. A 4.5-gallon bucket therefore covers roughly 450 sq ft. This calculator divides your total board area by 450 and rounds up to whole buckets.
Do I subtract doors and windows from drywall area?
Yes. You hang no board where an opening is: this calculator deducts 21 sq ft per standard door and 15 sq ft per standard window before counting sheets.
How much waste should I add for drywall?
10% covers normal cutting waste in rectangular rooms. Raise it to 15% for rooms with angled walls, closets, or many openings, where offcuts are rarely reusable.