Free drywall calculator: enter your room length, width and height, choose whether you're boarding the ceiling, and instantly get the drywall sheets, joint compound, tape and screws needed to board and finish the job. Add your board, compound, tape and screw prices for a full material or installed cost estimate. Works in imperial and metric.
Openings (deducted from walls)
Common: 8 / 9 / 10 / 12 ft long × 4 ft wide.
Enter your prices - leave any blank to skip it. The board count comes from your rooms above; for the screws, compound and tape, set the pack you're buying and the calculator works out how many. Covers the board, screws, compound and tape only; corner bead, insulation, sanding and paint are extra.
Boarded area
472.0 sq ft
Screws
~544
Joint compound
~62 lb
Joint tape
~175 ft
Drywall (plasterboard) is sold in sheets that clad the studs, then the joints between them are taped and filled. The calculator sizes both the boarding and the finishing from your room dimensions:
wall area = 2 × (length + width) × height - openings
ceiling = length × width (if you board it)
sheets = ceil( (wall area + ceiling) × wastage ÷ sheet area )
screws = sheets × 32
compound = boarded area × 0.64 kg/m²
tape = boarded area × 1.2 m/m²
By default the wall area treats the room as a closed box. Add the doors and windows on each room and the calculator subtracts their area from the walls - handy when a room has large openings that would otherwise have you buying boards you only cut to waste. Leave the openings off for a quick closed-box estimate where the wastage allowance covers the offcuts.
This example follows the unit system you pick in the calculator above.
A 12 × 10 ft room, 8 ft high, ceiling boarded, with 8 × 4 ft sheets and 10% wastage:
| Item | Rule of thumb |
|---|---|
| Screws | ~32 per sheet (8-12 in spacing); ceilings need more |
| Joint compound | ~0.13 lb/sq ft for a taped three-coat finish |
| Joint tape | ~1 ft per 3 sq ft of board |
| Corner bead | The length of each external corner, bought separately |
In the United States, drywall is typically sold as 4 × 8 ft and 4 × 12 ft sheets, usually 1/2 in thick, fixed to studs at 16 in centres and finished with joint compound (mud) over the joints. Pick the board size you are actually buying in the calculator above so the sheet count matches what is on the shelf.
For the recognised installation and finishing detail - fastener spacing, joint treatment and the levels of finish - see the Gypsum Association's GA-216 Application and Finishing of Gypsum Panel Products.
Work out the area to board - the walls are the room perimeter times the ceiling height, plus the ceiling itself if you are boarding it - then divide by the area of one sheet and add wastage. A 12 × 10 ft room 8 ft high with the ceiling boarded comes to 472 sq ft; with 4 × 8 ft sheets and 10% wastage that is 17 sheets. Enter your room and sheet size above for the exact figure.
Allow roughly 0.13 lb of joint compound per square foot of board for a taped, three-coat finish - about a 4.5 gallon (61.7 lb) box per 475 sq ft. For tape, allow about 370 linear feet per 1,000 sq ft. The calculator works both out from your boarded area.
Around 32 screws fix a standard 4 × 8 ft sheet to studs at 16 inch centres - roughly a screw every 8-12 in around the edges and down the centre studs. Ceilings are fixed more densely. The calculator multiplies your sheet count by 32 as a buy estimate.
If you are drywalling a ceiling as well as the walls, tick "Board the ceiling" on each room and the calculator adds the floor area (length × width) to the boarded total. Board the ceiling first so the wall sheets tuck up under it and support the edges. Leave it unticked for a walls-only job.
Add each door and window to the room and the calculator deducts its area from the walls before working out the sheets. Use the "+ Door" and "+ Window" buttons for a standard size, then edit the width, height and quantity to match. For a small room with one or two openings you can skip this and let the wastage allowance cover the offcuts; deduct them when the openings are large enough to save a sheet or two.
Add 10% for a simple room and 15% where there are lots of doors, windows, alcoves or services to cut around. Offcuts from openings can often be reused lower down or above doors, but it is safer to round up than to be one sheet short and stop the job.
Turn a room size or a square-footage figure into a drywall sheet count.
Read guide→Work out joint compound and tape from your boarded area, in boxes and rolls.
Read guide→Estimate drywall labor and material cost per square foot and per sheet.
Read guide→Studs, plate/track and drywall sheets for a partition wall, with cost built in.
Open calculator→Batt, roll or blown-in bags - and cost - to hit a target R-value for your walls, attic and ceilings.
Open calculator→Gallons or litres of paint for walls and ceilings, with coats and coverage built in.
Open calculator→How many tiles, boxes, adhesive and grout to buy for a floor or wall, with wastage and cost built in.
Open calculator→Linear feet of baseboard and how many stock lengths to buy.
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