Drywall Calculator

What is a drywall calculator?

A drywall calculator tells you how many sheets of drywall (also called gypsum board, plasterboard, or wallboard) you need to cover a wall or ceiling of a given size. You enter the surface’s length and height in feet, and the calculator returns the sheet count for the two most common sheet sizes so you can order a single delivery instead of measuring and counting by hand.

Knowing the sheet count up front lets you price the job, plan your cuts, and avoid both running short mid-project and overpaying for surplus board.

How does it work?

First, the calculator finds the total surface area. A rectangular wall or ceiling that is $L$ feet long and $H$ feet high has an area of:

Each drywall sheet covers a fixed amount of that area:

• A 4×8 ft sheet covers $4 \times 8 = 32 \text{ ft}^2$.
• A 4×12 ft sheet covers $4 \times 12 = 48 \text{ ft}^2$.

The number of sheets is the total area divided by one sheet’s coverage, rounded up to the next whole sheet, because you cannot buy a fraction of a board:

So the two sheet counts are:

The larger 4×12 sheets cover more area each, so they always give a lower piece count — handy on long, open walls where fewer seams mean less taping and mudding.

Worked examples

A 12 ft by 8 ft wall. The area is $12 \times 8 = 96 \text{ ft}^2$. Dividing by 32 gives exactly $3$, so you need 3 sheets of 4×8 ft board. Dividing by 48 gives exactly $2$, so the same wall takes 2 sheets of 4×12 ft board.

A 20 ft by 10 ft wall. The area is $20 \times 10 = 200 \text{ ft}^2$. For 4×8 sheets, $200 / 32 = 6.25$, which rounds up to 7 sheets. For 4×12 sheets, $200 / 48 = 4.17$, which rounds up to 5 sheets — the partial final sheet covers the leftover strip of wall.

Practical notes

• Buy extra for waste. The count above is the bare minimum that exactly tiles the area. Add roughly 10–15% for cuts around corners, outlets, and breakage. On the 7-sheet wall, that means picking up about 8 sheets.
• This estimator does not deduct openings. Doors and windows are not subtracted. For a large opening, compute its area in square feet and divide by your sheet’s coverage to see how many sheets you can save.
• Pick the sheet size that fits your space. Longer 4×12 sheets reduce seams but are heavier and harder to maneuver up stairs or in tight rooms; 4×8 sheets are easier to handle solo.
• Pair it with related tools. Confirm your surface area with the square footage calculator, or estimate other wall materials with the concrete block calculator and the brick calculator.

Frequently asked questions

How many 4×8 sheets are in 100 square feet? Each 4×8 sheet covers 32 ft², so $100 / 32 = 3.125$, which rounds up to 4 sheets.

Should I use 4×8 or 4×12 sheets? Use 4×12 sheets on long, open walls and ceilings to cut down on seams and finishing work. Use 4×8 sheets in smaller rooms or when you are working alone, since they are lighter and easier to position.

Does the calculator account for doors and windows? No. It estimates full coverage of the rectangle you enter. Subtract large openings separately if you want to trim the order.