Drywall Calculator
Work out drywall sheets for a room from wall and ceiling area, plus the joint compound, tape and screws needed, using standard trade estimating ratios.
Board area = 2 × (length + width) × height, plus the ceiling, less standard door and window allowances, with a 10% waste allowance. Finishing materials use the common estimating ratios of about 138 lb of joint compound, 400 ft of tape and one screw per square foot for every 1,000 sq ft of board (a three-coat finish; level 5 uses more). Framing spacing, corner beads and offcut reuse all shift the real figures. Estimates only.
What is the Drywall Calculator?
The ByteTools Drywall Calculator sizes a plasterboard job. Enter the room dimensions, choose whether the ceiling is included, deduct doors and windows, and pick your sheet size — 4×8, 4×10 and 4×12 in imperial, or 1200 × 2400, 2700 and 3000 mm in metric — and it returns the board area and the number of sheets to buy with a waste allowance.
- Wall and ceiling area with door and window deductions
- Sheet sizes in both imperial and metric formats
- Waste allowance, 10% by default
- Joint compound in pounds, kilos and 4.5-gallon buckets
- Joint tape in feet, metres and 250 ft rolls, plus screw count
- Runs offline in your browser — nothing uploaded
How to use the Drywall Calculator
- 1
Choose imperial or metric and enter the room length, width and wall height.
- 2
Enter the number of doors and windows to deduct and tick the ceiling if you are boarding it.
- 3
Select the sheet size you plan to buy and set the waste allowance.
- 4
Read the sheet count, then the joint compound, tape and screw estimates below it.
About the Drywall Calculator
The ByteTools Drywall Calculator sizes a plasterboard job. Enter the room dimensions, choose whether the ceiling is included, deduct doors and windows, and pick your sheet size — 4×8, 4×10 and 4×12 in imperial, or 1200 × 2400, 2700 and 3000 mm in metric — and it returns the board area and the number of sheets to buy with a waste allowance.
It then estimates the finishing materials using the common trade ratios of roughly 138 lb of joint compound, 400 feet of tape and one screw per square foot for every 1,000 square feet of board, converted into buckets, rolls and an approximate screw weight.
Everything is calculated in your browser and nothing is uploaded. Framing spacing, corner beads, the finish level you are aiming for and how well you reuse off-cuts all shift the real quantities, so treat these as planning estimates. Moisture-resistant and fire-rated boards cost more but are counted exactly the same way here.
Frequently asked questions
How many sheets of drywall do I need for a 12x12 room?
A 12 ft by 12 ft room with 8 ft walls has 384 sq ft of wall plus 144 sq ft of ceiling. Deducting a door and two windows leaves about 478 sq ft, which is 526 sq ft with 10% waste — around 17 sheets of 4×8. Enter your own room above for an exact count.
How much joint compound do I need per sheet of drywall?
A three-coat finish uses roughly 138 lb of ready-mixed compound per 1,000 square feet of board, which works out at about 4.4 lb for a 4×8 sheet. A level 5 skim coat uses noticeably more, and setting-type compound behaves differently again.
How much drywall tape do I need?
Plan for about 400 linear feet of tape per 1,000 square feet of board — roughly 12 to 13 feet per 4×8 sheet. A standard 250 ft roll therefore covers around 625 square feet of drywall, or about 20 sheets.
How many screws per drywall sheet?
About one screw per square foot of board, so roughly 32 screws for a 4×8 sheet fixed to framing at 16 inches on centre. Ceilings are usually fixed more densely, and 12-inch spacing pushes the count higher.
Should I use bigger drywall sheets?
Longer sheets mean fewer butt joints, which are the hardest joints to finish invisibly, so 4×12 boards give a better result on long walls. They are also heavy and awkward to carry and lift alone, which is why 4×8 remains the DIY default.
Related tools
Paint Calculator
Work out how much paint a room needs from its length, width and height, minus doors and windows, with coats, coverage rate and the number of cans to buy.
Tile Calculator
Calculate how many tiles and boxes you need for floors or walls from tile size, grout joint width and a waste allowance, across as many surfaces as you like.
Wallpaper Calculator
Calculate wallpaper rolls from room size, roll width and length, and pattern repeat — with pattern matching, trim allowance and the real waste percentage shown.
Board Foot Calculator
Calculate board feet for a whole lumber cut list from thickness, width and length, with quantities, a cubic-metre equivalent and cost per board foot.
Area Calculator
Calculate the area of a rectangle, triangle, circle, trapezoid or ellipse from simple measurements, with the formula shown and results in m², ft² and more.