Inputs to result
Wall area = 2 × (length + width) × height; ceiling area = length × width; net area = (wall area + ceiling area) − deductions; sheets = ceil(net area ÷ sheet area × (1 + waste% ÷ 100)).
Carpentry & Framing
Drywall Calculator
Calculate 4x8 and 4x12 drywall sheet counts, joint compound, screws, and tape from room dimensions, ceiling height, and openings.
Enter the room length, width, ceiling height, and door/window openings, then select sheet dimensions. The calculator estimates total sheets, joint compound, tape, and screws.
Calculation and worked example reviewed 2026-11-12. See our calculation methodology.
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Carpentry & Framing
US UNITSEnter your measurements
YOUR ESTIMATE
29 sheets to order818 sq ft net surface25.6 sheets (4×8 ft) before 10% waste.
Est. accessories: 2.3 pails (4.5 gal) compound · 1015 ft tape · 2 lb screws.
Formula and example
How this calculation works
This estimator converts your entered jobsite inputs (room length, room width, ceiling height, include ceiling, drywall sheet size, door and window openings, waste allowance) into consistent US trade units, computes the exact geometric baseline first, and then applies any selected waste or order allowance so you can verify both numbers before purchasing materials.
How does the drywall calculator formula work?
Wall area = 2 × (length + width) × height; ceiling area = length × width; net area = (wall area + ceiling area) − deductions; sheets = ceil(net area ÷ sheet area × (1 + waste% ÷ 100)).
(Drywall Calculator)where:
- Room length – Entered in ft (default reference: 20 ft);
- Room width – Entered in ft (default reference: 15 ft);
- Ceiling height – Entered in ft (default reference: 8 ft);
- Include ceiling – Entered in selected option (default reference: yes );
- Drywall sheet size – Entered in selected option (default reference: 4x8 );
- Door and window openings – Entered in sq ft (default reference: 42 sq ft);
- Waste allowance – Entered in % (default reference: 10 %);
Check the math
A 20 ft × 15 ft room with 8 ft ceilings and one 42 sq ft opening has 518 sq ft wall area + 300 sq ft ceiling = 818 sq ft. At 10% waste, order twenty-nine 4 × 8 ft sheets (32 sq ft each).
Quick lookup chart
Drywall Sheet & Accessory Estimates by Room Size (8 ft Ceilings)
Estimates include walls and ceiling for rectangular rooms using standard 4 × 8 ft sheets and 10% waste.
| Room Dimensions | Surface Area (Walls + Ceiling) | 4 × 8 Sheets (w/ 10%) | Joint Compound & Screws |
|---|---|---|---|
| 10 ft × 10 ft | 420 sq ft | 15 sheets | 1 pail (4.5 gal) · 1 lb screws |
| 12 ft × 15 ft | 592 sq ft | 21 sheets | 2 pails (4.5 gal) · 2 lb screws |
| 15 ft × 20 ft | 820 sq ft | 29 sheets | 3 pails (4.5 gal) · 2 lb screws |
| 20 ft × 24 ft | 1,144 sq ft | 40 sheets | 4 pails (4.5 gal) · 3 lb screws |
Before you use this result
This is a square-footage sheet estimate. Butt joints, framing layout, bevels, drywall thickness (1/2 in vs 5/8 in Type X), fire ratings, and complex soffits require field layout verification.
- Hang ceiling drywall first before walls to ensure snug, supported wall-to-ceiling perimeter joints.
- Install drywall sheets horizontally perpendicular to studs/joists to maximize shear strength and minimize finished seam length.
- Use 1-1/4 in coarse-thread drywall screws for 1/2 in drywall on wood studs, spaced 12 in on ceilings and 16 in on walls.
Questions answered
Calculator FAQ
How many square feet does a 4 × 8 sheet of drywall cover?+
A standard 4 × 8 ft sheet covers 32 square feet. A larger 4 × 12 ft sheet covers 48 square feet and reduces the number of finished butt joints by roughly 25%.
How much drywall compound (mud) and tape do I need?+
Plan roughly one 4.5-gallon pail of premixed joint compound per 350–400 sq ft of drywall (or ~1 gallon per 100 sq ft). Order about 35 feet of joint tape per 4 × 8 sheet.
Should I subtract windows and doors from drywall estimates?+
Yes, enter the combined opening area. However, keep waste at 10% to 15% because cutouts around doors and windows still produce offcuts that cannot always be reused.