How it works
Wall area = room perimeter × wall height. Add the ceiling if selected, subtract openings, add waste, then divide by the sheet's area: 32, 40 or 48 sq ft. Sheets round up.
The 4 × 8 ft, 4 × 10 ft or 4 × 12 ft sheets are common sizes; check your store.
Worked example
A 12 × 12 ft room with 8 ft walls and its ceiling, no openings: walls 2 × (12 + 12) × 8 = 384 sq ft, plus the ceiling 144 sq ft = 528 sq ft. With 10% waste that is 19 sheets of 4 × 8 ft, 15 of 4 × 10 ft or 13 of 4 × 12 ft.
Tips and common mistakes
- Measure wall height from floor to ceiling.
- Enter each door and window you will not cover.
Questions about this calculator
How do I calculate how much drywall I need?
Add the wall areas (perimeter × height) and the ceiling, subtract doors and windows, add waste, and divide by the sheet area.
How many sq ft is a 4x8 sheet of drywall?
32 sq ft.
How much drywall do I need for a 12x12 room?
With 8 ft walls and the ceiling, and no openings, it is 528 sq ft. That is 17 sheets of 4×8, or 19 with 10% waste. Subtract doors and windows for your own room.
Sources
Values marked with a link come from the linked source, which opens in a new tab. Unit conversions and our own defaults are listed separately. Every value the site uses is in the methodology source register.
Where the numbers come from 1
- Meters per international foot
- 0.3048 m/ft
- NIST, international foot conversion (opens in a new tab)nist.gov
Unit conversions and our defaults9
- Centimeters per meter
- 100 cm/m
- Metric prefix definition: centi is one hundredth
- Percent denominator
- 100 %
- Definition of percent: parts per hundred
- Common drywall sheet lengths
- 8, 10, 12 ft (4 ft wide)
- Common sizes — check your store. A 4 ft wide sheet covers 4 × its length in square feet
- Drywall sheet width
- 4 ft
- Common sizes — check your store
- Drywall waste default
- 10 %
- Owner planning default; editable
- Drywall calculator starting room
- 12, 12, 8 ft length, ft width, ft wall height
- Wave 2 pack worked example; editable starting measurements
- Rooms that can be added in one estimate
- 8 rooms
- Build choice: keeps the form manageable; run the tool again for more rooms
- Count rounding tolerance
- 1e-9 unitless
- Owner specification: ceil(x − 1e-9)
- Volume and weight display precision
- 2 decimal places
- Owner specification: display volume and tons to two decimals