About the Drywall Calculator
Buying too little drywall means a second trip to the shop, and buying too much costs money. This calculator takes the length, width and height of a room, subtracts doors and windows, can add the ceiling, adds a waste allowance and divides by the size of the sheet you use. It gives the number of whole sheets and a rough count of screws. Type the room size, the area of openings, the sheet size and the waste and the drywall sheets appears at once, with a few related figures underneath, and you can copy the result with one tap. The sums run in your browser, so nothing you enter is uploaded.
Updated October 2026
How to use the Drywall Calculator
- 1Enter the room size, the area of openings, the sheet size and the waste.
- 2Pick the units or options from the menus if the drywall sheets tool offers them.
- 3Read the drywall sheets in the large result box.
- 4Look at the extra rows for related figures.
- 5Press Copy result to keep the answer.
When you need the drywall sheets
Home owners and builders use it to order materials, compare the cost of different sheet sizes and plan deliveries. Larger sheets mean fewer joints, but are heavier and need two people on walls.
Waste depends on the layout and the skill of the fitter. Rooms with many corners, odd shapes or openings cut more offcuts, so 10 to 15 percent is a safe figure. A simple rectangular room can use 5 to 8 percent.
How the drywall sheets is worked out
Area = 2 × (length + width) × height − openings, plus length × width for the ceiling. Sheets = area × (1 + waste) ÷ sheet area, rounded up. Screws are about one per square foot. A room 12 ft by 10 ft with 8 ft walls has 352 sq ft of wall. Take off 40 sq ft of doors and windows, add the 120 sq ft ceiling, and you have 432 sq ft. With 10 percent waste and 4 × 8 ft sheets of 32 sq ft you need 15 sheets and about 480 screws.
Every answer on this page comes from that one rule, so you can check any result by hand with a calculator. The figures shown underneath, such as other units, are conversions of the same answer.
- Feet or metres
- Four sheet sizes
- Waste allowance and screw count
Mistakes to avoid with drywall sheets
Remember to enter the total area of doors and windows, not just one. Also, do not forget to add the joint compound, tape and corner bead, which this tool does not count. Check whether your local sheets are 4 ft by 8 ft or 1.2 m by 2.4 m.
On phone and computer
On a phone, type into the boxes one after another and read the drywall sheets underneath; Copy result puts it on the clipboard for a message or a note. On a computer the inputs sit on the left and the answer on the right, so you can change one figure and watch the drywall sheets move. The drywall calculator works the same on both. Finishing a room involves other materials. Calculate paint with Paint Calculator, the floor with Flooring Calculator, tile with Tile Calculator, and use Area Calculator for any wall you are measuring by hand.
Features
- Add 10 to 15 percent waste
- Subtract large openings
- Buy tape and compound separately
- Clear messages when the drywall sheets inputs make no sense
- Copy the result with one tap
- Private: nothing is uploaded
Frequently asked questions
How do I calculate drywall sheets?
Area = 2 × (length + width) × height − openings, plus length × width for the ceiling. Sheets = area × (1 + waste) ÷ sheet area, rounded up. Screws are about one per square foot. A room 12 ft by 10 ft with 8 ft walls has 352 sq ft of wall. Take off 40 sq ft of doors and windows, add the 120 sq ft ceiling, and you have 432 sq ft. With 10 percent waste and 4 × 8 ft sheets of 32 sq ft you need 15 sheets and about 480 screws.
What is the formula for drywall sheets?
Area = 2 × (length + width) × height − openings, plus length × width for the ceiling. Sheets = area × (1 + waste) ÷ sheet area, rounded up. Screws are about one per square foot. The drywall calculator applies it exactly and rounds only the displayed answer to six significant figures.
Should I subtract openings?
Yes, but only large ones. Small openings like sockets are ignored, and very small windows may not be worth subtracting because offcuts are used for them.
How many screws per sheet?
About 32 for a 4 by 8 foot sheet, spaced roughly every 12 to 16 inches. The calculator scales this to the sheet size.
What thickness should I choose?
Walls are usually 12.5 mm (½ inch), ceilings 12.5 mm or 15 mm (⅝ inch). The thickness does not change the number of sheets.
Is this drywall calculator free and private?
Yes. It is free, needs no account and runs in your browser, so the numbers you type are not uploaded or stored.