Logo

MonoCalc

/

Drywall Calculator

Construction

Units

Sets result units, sheet sizes, framing and packaging defaults you haven't changed, and the units for new surfaces. Surfaces you have entered keep their own units.

Identical surfaces, e.g. 3 matching bedrooms.

Measure along the floor, wall to wall. Wall height is floor to ceiling.

Openings

Door and window sizes are a typical size, measure yours. Set the count to 0 if there are none.

W

H

W

H

Not to scale

full sheet

cut piece

Illustrative layout. The purchase count pools offcuts across the whole job.

Walls: net area = 2 × (L + W) × H − openings

—

1 of 30 surfaces

Many drywall hangers don't deduct windows and doors, because the cut-outs are mostly waste. Turn this off for a more generous count.

Sheets and framing

Walls and ceilings are set up separately: they are often hung with different sheet lengths or thicknesses, and ceilings need closer screw spacing.

Walls

Labels the shopping list only.

5/8 in (15 mm) fire-rated board is often required on garage walls shared with the house and on some ceilings. Check your local code.

Hanging direction

US practice usually runs sheets horizontally. UK and Australian practice often runs 1200-wide boards vertically, with the edges on studs. This changes the drawing and the screw count, never the sheet count.

in

Waste

10% suits simple rectangular rooms. Use 15% or more for lots of openings, angles or short wall runs.

Only changes the symbol; nothing is converted.

Finishing materials

Screws, joint compound, tape and corner bead, worked out from the net board area (before waste).

Joint compound (all-purpose, ready-mixed)

If your compound is sold by weight, use the coverage printed on the bag.
gal
$

Joint tape (paper)

ft
$

Screws

Counted per sheet from the framing and screw spacing of each group.

Leave empty to see the count only.
$

Corner bead (outside corners)

Each corner gets its own continuous pieces, so a 9 ft corner with 8 ft bead needs 2 pieces. Pieces are never pooled across corners.

ft

No outside corners yet.

Results

Enter your room or wall sizes to see how many sheets you need.

About This Tool

Drywall Calculator – How Many Sheets, Screws and Buckets of Mud

A drywall calculator turns room measurements into a shopping list. This one counts the sheets of drywall (plasterboard) for your walls and ceilings. It then compares sheet sizes and adds the finishing materials: screws, joint compound, paper tape and corner bead. Each surface is also drawn to scale with the sheets laid over it, so you can see how the boards will go up before you buy them.

Measuring a Room for Drywall

Measure the length and width of the room along the floor, wall to wall, and the wall height from floor to ceiling. The wall area is the perimeter times the height: 2 × (L + W) × H. A 12 × 12 ft room with 8 ft walls has 2 × 24 × 8 = 384 ft² of wall. Add single walls, the triangular gable ends under a pitched roof (base × peak ÷ 2) and ceilings as separate surfaces. For sloped attic ceilings and stair walls, work out the area and enter it as a known area.

The Area-Plus-Waste Method

Professional estimators don't count sheets wall by wall. Offcuts from one wall get used on the next, so a wall-by-wall count badly over-buys. Instead, the calculator adds up the net area of all the walls, adds a waste allowance, and divides by the area of one sheet: sheets = ⌈area × (1 + waste) ÷ sheet area⌉. For the room above, minus a door and a window, that is 349 ft² × 1.10 = 383.9 ft² ÷ 32 ft² = 12 sheets of 4×8. The layout diagram is only an illustration and never used for the count.

How much waste to allow
10% suits simple rectangular rooms. Use 15% or more for rooms with lots of openings, angled walls or short runs, where more of each sheet ends up as scrap.

Horizontal or Vertical Hanging

In the US, wall sheets are usually hung horizontally, with the long edge across the studs. This leaves fewer joints, and the seam between the two rows sits at a comfortable working height. In the UK and Australia, 1200 mm boards are often hung vertically, with every edge landing on a stud. The direction doesn't change how much board you need, but it does change the layout and the screw count. Ceiling sheets always run across the joists.

Choosing a Sheet Length to Cut Butt Joints

The ends of a sheet are not tapered, so where two ends meet (a butt joint) is the hardest seam to finish flat. Longer sheets mean fewer of these joints. A 12 ft wall covered with 4×12 sheets has none, while 4×8 sheets leave one in every row. Longer sheets are heavier and harder to get through doors and up stairs, though. The sheet-size comparison shows how many sheets each length needs. If you enter prices, it also shows which size is cheapest for your job.

Thickness and Fire-Rated Board

Standard 1/2 in (12.5 mm) board is the usual choice for walls and most ceilings. 5/8 in (15 mm) fire-rated board is stiffer and resists fire for longer. Building codes often require it on garage walls shared with the house and on some ceilings. Thinner 1/4 and 3/8 in board is for curved walls and for covering old walls. The calculator uses thickness only to label the shopping list, since it doesn't change the sheet count.

Finishing Materials

Finishing is worked out from the installed board area, before waste. The default rates are rules of thumb:

  • Joint compound: about 1 gal per 100 ft² of ready-mixed all-purpose compound (≈ 0.41 L/m²) for taping and two finishing coats.
  • Paper tape: about 37 ft per 100 ft² (≈ 1.21 m/m²).
  • Screws: counted per sheet from the framing and screw spacing. For example, 28 for a 4×8 wall sheet on 16 in studs.
  • Corner bead: counted per outside corner, rounded up to whole pieces.
Check your product's coverage
Coverage varies between brands and between ready-mixed, lightweight and powder compounds. If your compound is sold by weight, replace the default rate with the coverage printed on the bag.

Frequently Asked Questions

Is the Drywall Calculator free?

Yes, Drywall Calculator is totally free :)

Can I use the Drywall Calculator offline?

Yes, you can install the webapp as PWA.

Is it safe to use Drywall Calculator?

Yes, any data related to Drywall Calculator only stored in your browser (if storage required). You can simply clear browser cache to clear all the stored data. We do not store any data on server.

How many sheets of drywall do I need for a 12 × 12 room?

With 8 ft walls, a 12 × 12 ft room has 384 ft² of wall. Take off one door and one window (about 35 ft²) and you have 349 ft². Add 10% waste and you need 383.9 ft², which is 12 sheets of 4×8 or 8 sheets of 4×12. Board the ceiling as well and you need 4 more 4×12 sheets for its 144 ft².

Should I subtract windows and doors?

It depends on how generous you want the count to be. Subtracting them gives the tightest estimate. Many drywall hangers don't bother, because the board cut out of an opening is mostly waste anyway. Turn off Deduct openings for the more generous count: for the 12 × 12 room it goes from 12 to 14 sheets of 4×8.

Should I buy 4×8 or 4×12 sheets?

Longer sheets mean fewer butt joints to tape and often fewer sheets. A 12 ft wall can be covered with no butt joints at all. They are heavier and harder to carry up stairs, though, and a 4×8 can be hung by one person. Enter prices for both and the calculator shows which size is cheaper for your job.

How much joint compound and tape do I need?

A common rule of thumb is about 1 gallon of ready-mixed all-purpose compound and 37 ft of paper tape per 100 ft² of board, which works out to roughly one 4.5 gal pail per 450 ft². In metric that is about 0.41 L and 1.21 m per m². Both rates can be changed to match your product.

How many screws per sheet of drywall?

It depends on the framing and screw spacing. A 4×8 sheet hung horizontally on studs 16 in apart, with screws every 16 in, crosses 7 studs with 4 screws each: 28 screws. A 4×12 ceiling sheet on joists 16 in apart, with screws every 12 in, takes 10 × 5 = 50.

What thickness of drywall should I use?

1/2 in (12.5 mm) is the usual choice for walls and most ceilings. 5/8 in (15 mm) fire-rated board is stiffer and is often required on garage walls shared with the house and on some ceilings. Thinner 1/4 and 3/8 in board is for curves and covering old walls. Check your local building code.