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Drywall, Flooring & Interior

Drywall Calculator

Sheets, screws, joint compound and tape for a room, with doors and windows deducted.

Your measurements

Enter the room; ceilings can be included or left out.

Room
Floor to ceiling. Most rooms are 8 ft; older houses are often 9 or 10.
Openings and board
Longer sheets mean fewer butt joints, which are the hardest joints to hide.

Your result

Sample values

18

Sheets of 4 × 12

790

Net area, ft²

5

Boxes of screws

9

Gallons of compound

Walls and ceiling, 10% waste, two doors and two windows deducted.

What to order

Item Quantity
4 × 12 sheets, 1/2 in 18 sheets
Joint compound 9 gallons
Paper tape 360 ft
1-1/4 in screws 5 lb
Corner bead 4 lengths

How to use this calculator

Enter the room dimensions and wall height, then say whether the ceiling is going on too. Doors and windows are deducted at standard sizes; if yours are unusual, subtract the extra area from the room length as a rough adjustment.

Pick the largest sheet you can physically get into the room and lift. A 4 × 12 sheet weighs around 80 lb in half inch board and needs two people, but it removes butt joints from an ordinary wall entirely, which saves far more time in finishing than it costs in handling.

Formula

Wall area = Perimeter × Height

Net area = Wall area + Ceiling − Openings

Sheets = Net area ÷ Sheet area × (1 + Waste)

Perimeter
2 × (Length + Width)
Openings
21 ft² per door, 12 ft² per window

Compound and tape are estimated from the joint length, which scales with sheet count.

Worked example

A 14 ft by 12 ft room, 8 ft ceilings, ceiling included, two doors and two windows, 4 × 12 sheets, 10% waste.

  1. Perimeter: 2 × (14 + 12) = 52 ft
  2. 52 ft × 8 ft = 416 ft² of wall
  3. 14 × 12 = 168 ft² of ceiling
  4. Openings: (2 × 21) + (2 × 12) = 66 ft²
  5. 416 + 168 − 66 = 518 ft² net
  6. 518 ft² × 1.10 = 570 ft² with waste
  7. 570 ÷ 48 ft² per sheet = 12 sheets for walls and ceiling

18 sheets allowing for cut waste around openings

Understanding your results

The sheet count is the firm number; compound and screws are estimates that depend on how you work. A three coat finish over paper tape uses noticeably more compound than a light skim over mesh, and a level 5 finish across a whole room can double it.

Deducting openings is slightly optimistic on purpose. You cannot use the offcut from a door opening anywhere else on the job, so the waste allowance is doing real work here rather than covering carelessness. A room with many small windows should be run at fifteen percent.

Questions

About this calculator

Ask something else

Yes. Hanging the ceiling first lets the wall sheets push up underneath and support the ceiling edge, which takes the load off the fasteners and closes the joint neatly. Doing it the other way round leaves a gap that has to be filled.

Horizontal on ordinary 8 ft walls. It puts the tapered joint at a comfortable working height, produces one long seam instead of several vertical ones, and the seam runs across the studs, which stiffens the wall. Vertical suits high walls and commercial fire rated assemblies.

Five eighths is heavier, stiffer and carries a fire rating, so it is required on garage ceilings under living space and on many party walls. It also sags less on ceilings framed at 24 in centres. Half inch is the default everywhere else.

Around half a gallon per sheet for a standard three coat finish, which is where the nine gallon figure comes from. Buy the larger bucket rather than several small ones; leftover compound keeps for months if the surface is smoothed and covered with a film of water.

Keep going

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Estimates, not specifications. Results are based on the values you enter and on typical material properties. Densities, coverage rates and product sizes vary between suppliers, so confirm quantities against your supplier's data before ordering. Structural work must be signed off by a qualified professional and meet your local building code.