Use this drywall calculator to turn rectangular room dimensions or a known wall and ceiling surface area into whole panels, with separate estimates for joint tape, compound, and Type W screws.
Measure walls and ceilings before choosing a panel size
Room floor area is not drywall area. Measure the wall and ceiling surfaces that will receive panels, or enter a covered-area total you already trust. The calculator keeps the optional large-opening deduction separate so you can see gross and net area.
For four rectangular walls, use the room perimeter and wall height. The OpenStax rectangle formulas provide the geometry basis. Add the ceiling only when it will receive drywall.
Room mode calculates the selected surfaces. Known-area mode expects their combined surface area, not the building's floor area.
USG J371 describes subtracting large doors and picture windows while ignoring small electrical and pipe cutouts. The field stays at zero unless you enter an aggregate deduction.
Example: a rectangular room with walls and ceiling
- Enter 12 ft long, 10 ft wide, and 8 ft high, choose walls and ceiling, select 4 × 8 panels, and leave openings and extra allowance at 0.
- The engine calculates 352 sq ft of wall area and 120 sq ft of ceiling area, for 472 sq ft total.
- One panel covers 32 sq ft, so the exact equivalent is 14.75 panels.
- The calculator rounds that up to 15 panels.
Panel coverage for common drywall sheet sizes
Panel face area is the divisor in the whole-panel calculation. Choose the stock size you will actually buy.
| Panel size | Area per panel | Metric equivalent |
|---|---|---|
| 4 × 8 | 32 | 2.97 |
| 4 × 10 | 40 | 3.72 |
| 4 × 12 | 48 | 4.46 |
Panel dimensions and square-foot coverage follow USG J371. Metric equivalents use the exact NIST foot conversion and the shipped engine.
How the calculator turns area into whole drywall panels
The engine subtracts the entered large-opening area first, then applies the extra allowance to net area. It divides that adjusted purchase area by the selected panel area. An exact whole quotient stays unchanged; a positive fraction rounds up to the next purchasable panel. The USG Wallboard Estimator says its estimate does not include waste, so this calculator starts at 0% and leaves the allowance visible and editable rather than claiming one universal rate.
What the tape, compound, and screw estimates assume
The finishing estimates use net covered area before extra panel allowance. At 1,000 sq ft, the shipped engine returns 370 ft of joint tape, 10 gal of All Purpose compound, 9 gal of Plus 3 compound, and 2.7 of Type W screws. These values reconcile exactly to the USG J371 typical-room table. For smaller jobs, the Type W result uses the next published 100 sq ft table band; above 1,000 sq ft, it scales the 2.7 lb row and labels that basis as an extrapolation. Type W is the table's wood-framing fastener, using 12 in ceiling spacing and 16 in wall spacing, not a fastening schedule for every assembly. Choose either the All Purpose or Plus 3 compound estimate, not both. J371 bases those typical-room compound quantities on flat joints plus inside and outside corners with metal corner bead. USG says actual use can vary widely with the substrate, tools, application method, and job conditions.
Where an area-based drywall estimate stops
Area division cannot place seams, choose orientation, prove offcut reuse, or account for every supported edge. Panel type, thickness, moisture exposure, fire rating, framing, adhesive, and fastening pattern belong to the selected assembly and applicable documents. Pricing and labor also vary by project and location, so they require a separate cost estimate or contractor bid. Use this result as a material takeoff, not a layout, code decision, or quote.