Drywall Calculator
Find how many sheets of drywall (sheetrock) your room needs, plus joint compound, tape, screws, and cost.
How to use the drywall calculator
- 1
Enter your room's length, width, and wall height, and check "Include ceiling" if you're drywalling that too.
- 2
Enter the number of doors and windows, plus any other opening area, so they're subtracted from the total.
- 3
Choose your sheet size and a waste factor, and optionally turn on finishing materials and cost.
- 4
Your sheet count, joint compound, tape, screws, and cost appear instantly and update as you adjust any field.
How drywall quantities are calculated
Estimating drywall accurately means working through the room geometry step by step rather than guessing. Here's exactly how the calculator arrives at your number:
- Wall perimeter = 2 × (length + width)
- Gross wall area = perimeter × wall height
- Openings area = (doors × 21 sq ft) + (windows × 15 sq ft) + other openings
- Net drywall area = gross wall area + ceiling area (if included) − openings area
- Area with waste = net area × (1 + waste factor)
- Sheets needed = area with waste ÷ sheet coverage, rounded up
Worked example: A 12 ft × 10 ft room with 8 ft walls has a perimeter of 2 × (12 + 10) = 44 ft, giving a gross wall area of 44 × 8 = 352 sq ft. Subtracting one door (21 sq ft) and one window (15 sq ft) leaves 316 sq ft of net wall area. With a 10% waste factor, that's 347.6 sq ft to cover. At 32 sq ft per 4×8 sheet, you'd need 347.6 ÷ 32 = 10.9 sheets — rounded up to 11 sheets, since drywall is sold whole.
Sheet size and finishing material reference
| Sheet size | Coverage | Best for |
|---|---|---|
| 4 × 8 ft | 32 sq ft | Most rooms; easiest to handle solo |
| 4 × 10 ft | 40 sq ft | Taller walls, fewer seams |
| 4 × 12 ft | 48 sq ft | Long runs, garages, commercial |
| Material | Rule of thumb |
|---|---|
| Joint compound (mud) | ~1 gal per 100 sq ft, two coats |
| Joint tape | ~370 linear ft per 1,000 sq ft |
| Drywall screws | ~1.5 screws per sq ft (16" o.c. framing) |
Tips for estimating drywall accurately
Hanging sheets horizontally (running the long dimension along the wall) reduces the number of vertical seams, which means less taping, less mud, and a flatter finished wall — especially worthwhile on walls taller than 8 ft or longer than a single sheet.
It's almost always worth rounding up to the next full sheet, both because drywall is sold whole and because a little extra material on hand covers mistakes and future patch repairs without a second trip to the store.
For a smooth "level 5" finish (common under raking light or glossy paint), budget for a third skim coat of joint compound across the whole surface, not just the seams — this can roughly double the mud estimate above.
Once your walls are up and finished, our Paint Calculator uses the same room-geometry approach to estimate how much paint you'll need.
Doing a full material takeoff instead of just drywall? Try the Flooring Calculator →
Frequently asked questions
Related guides
How to figure out exactly how many sheets of drywall a room needs, why door and window deductions matter, and how sheet size changes the count.
Read the guide →How 4×8, 4×10, and 4×12 drywall sheets compare on coverage, seam count, weight, and when each size actually makes sense.
Read the guide →A complete overview of everything a drywall job needs — sheets, joint compound, tape, and screws — and how each quantity is calculated.
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