dopecalc

Drywall Calculator

Calculate the total square footage of drywall needed for a room including walls and ceiling. Estimate the number of 4×8 sheets, joint compound buckets, and tape rolls.

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About this Calculator

Calculate the total square footage of drywall needed for a room including walls and ceiling. Estimate the number of 4×8 sheets, joint compound buckets, and tape rolls.

Formula & Calculations

Formula

Wall Area = 2 × (Length + Width) × Height; Ceiling Area = Length × Width; Total Area = Wall Area + Ceiling Area; Sheets = Total Area / 32 (for 4×8 sheets, round up)
Where:
  • L=Room length in feet
  • W=Room width in feet
  • H=Room height in feet (typically 8 ft)
  • Sheets=Number of 4×8 drywall sheets needed

Assumptions

  • Standard drywall sheets are 4 feet × 8 feet (32 square feet each).
  • One gallon of joint compound covers approximately 100 square feet of taped seams.
  • One roll of drywall tape covers approximately 250 linear feet.
  • Does not subtract doors and windows; slightly overestimates which is good for safety.

Calculation Examples

Example 1

Inputs:Room: 12 ft × 10 ft × 8 ft (walls + ceiling)
Result:~472 sq ft total, ~15 sheets, ~5 gallons joint compound, ~2 rolls tape

Walls: 2×(12+10)×8 = 352 sq ft. Ceiling: 12×10 = 120 sq ft. Total: 472 sq ft. Sheets: 472/32 ≈ 14.75 → 15. Joint compound: ~5 gal. Tape: ~2 rolls.

Example 2

Inputs:Room: 15 ft × 12 ft × 9 ft (walls only)
Result:~486 sq ft walls, ~16 sheets, ~5 gallons joint compound, ~2 rolls tape

Walls: 2×(15+12)×9 = 486 sq ft. Sheets: 486/32 ≈ 15.2 → 16.

Frequently Asked Questions

What size drywall sheets should I use?

4×8 sheets are standard and easiest to handle. 4×12 sheets reduce seams on longer walls but are heavier. For 9-foot ceilings, 54-inch wide sheets (4.5×8 or 4.5×12) eliminate horizontal seams.

How much joint compound do I need per sheet?

As a rough rule of thumb, estimate 1 gallon of joint compound for every 100 square feet of drywall. This typically covers taping and finishing coats.

Should I subtract doors and windows?

This calculator does not subtract openings, which provides a small safety margin. Drywall pieces around openings often generate waste anyway, so the overestimate is practical.