Question 1

How do I calculate how many drywall sheets I need?

Accepted Answer

Calculate total wall area using 2 × (length + width) × ceiling height, add ceiling area (length × width) if needed, subtract door and window openings, then divide by your sheet size and add 10% waste. A 4×8 sheet covers 32 sq ft, so a 400 sq ft room with 10% waste needs ⌈440 ÷ 32⌉ = 14 sheets.

Question 2

Should I subtract doors and windows from my drywall calculation?

Accepted Answer

You can, but many professionals don't — drywall is hung over openings and cut out, so the cutoffs become waste. If you do subtract, use 21 sq ft per standard door (3×7 ft) and 15 sq ft per standard window (3×5 ft). For rooms with many openings, subtract them and increase waste to 15%.

Question 3

What size drywall sheets should I use?

Accepted Answer

4×8 ft sheets are standard for most residential work and easiest to handle solo. 4×12 ft sheets are preferred for ceilings and 9-foot walls — they span the full height horizontally with fewer joints to tape. 4×10 ft is a good middle ground for 9-foot walls.

Question 4

How much joint compound do I need?

Accepted Answer

Budget approximately 1 gallon of all-purpose joint compound per 100 square feet of drywall. A standard 5-gallon bucket covers about 500 sq ft for taping and two coats of mud. You'll need more for heavy texture or Level 5 finish.

Question 5

What thickness drywall should I use?

Accepted Answer

Use ½-inch drywall for standard interior walls and ceilings. Use ⅝-inch Type X (fire-rated) for garage walls and ceilings adjacent to living space — required by IRC. Use ¼-inch flexible drywall for curved walls. Moisture-resistant (green board) for bathrooms, though cement board is better behind tile.

Drywall calculator