Drywall calculator: how many sheets of drywall do I need?

How much drywall do I need? The math in words

1. Add the four walls: twice the length plus twice the width. That is the perimeter.
2. Multiply the perimeter by the wall height. That is the wall area.
3. Take off the doors and windows. The calculator starts at 21 square feet a door and 15 a window, the sizes Sherwin-Williams' training uses for openings in a wall.^[3]
4. Add the ceiling if it gets new board: length times width. Tick Include the ceiling.
5. Add the extra for cutting and piecing. Lowe's says to allow 10% to 15%, and USG's own sheet estimator leaves that allowance to you.^[1][4]
6. Divide by one sheet's area and round up. Drywall comes 4 feet wide and 8 to 16 feet long, so a 4 by 8 sheet is 32 square feet, a 4 by 10 is 40 and a 4 by 12 is 48.^[2]

Example: a 12 by 14 foot bedroom with 8 foot walls, one door, two windows and a new ceiling. Walls: 2 × (12 + 14) × 8 = 416 square feet, less 21 + 2 × 15 = 51 for the openings, leaves 365. The ceiling adds 12 × 14 = 168, so 533 square feet of board. Plus 10%: 586.3 square feet. In 4 by 8 sheets: 586.3 ÷ 32 = 18.3, so 19 sheets. In 4 by 12 sheets: 586.3 ÷ 48 = 12.2, so 13 sheets.

Which sheet size and how much extra

Longer sheets mean fewer joints to tape. Lowe's own estimating table lists 4 sheets of 4 by 8 or 3 sheets of 4 by 12 for 100 square feet of wall or ceiling, before the extra.^[1] Pick the sheet in the calculator and it divides by that sheet's area.

Lowe's range for the extra runs from 10% to 15%.^[1] The calculator starts at the bottom of it. A room cut up by a sloped ceiling, a stair or lots of corners sends more pieces to the bin, so set it toward the top.

Doors and windows: hangers often run a sheet straight over a small window and cut the opening out after, so the board is bought anyway. Set Windows to 0 if you hang that way; keep the doors, which leave a full-height gap.

Drywall from a floor plan, without retyping every wall

For a whole floor, go room by room: each room's perimeter times its wall height, less its own doors and windows, plus its ceiling. A wall between two rooms gets board on both sides, and the room-by-room math counts both sides, which is what you hang. Each room's ceiling is the same as its floor area: the square footage calculator adds those up, rectangle by rectangle.

A plan's whole-house wall area counts each wall once, one side, before doors and windows come out. On a PlaceAnew report it is a fair cross-check, and the rooms are what you order from. How to estimate materials from a floor plan works through drywall from one real scan.

Every wall and ceiling from one walk

Drywall takeoffs are slow because every wall, every height and every opening goes on paper first. PlaceAnew does that part in one walk. Hold an iPhone or iPad with LiDAR (iPhone 12 Pro or a newer Pro model, or an iPad Pro from 2020 or later), walk through the rooms, and the floor plan comes out with every room's size and area, every door and window, and the walls in 3D. The PDF report adds a property summary with the wall area, the average ceiling height and the door and window counts. Scanning, floor plans, 3D, editing, the kitchen designer with prices and exports are free.

The sizes hold up: in one walk of our own office, all seven wall lengths that compare one to one came within 2.5 inches of the hand-measured plan.^[5] Put each room's size from the plan into this calculator and the sheet count is done before you leave the house.

Questions people ask