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Drywall Calculator

Estimate the number of drywall sheets for your project.

Last updated: June 13, 2026

Calculator

feet
feet
feet

Results

Total Wall Area333 sq ft
4×8 Sheets Needed11 sheets
4×12 Sheets Needed7 sheets
Add 10% for waste13 sheets (4×8)

Recommended purchase amount

How to Use This Calculator

  1. 1Enter your room length and width in feet.
  2. 2Enter the ceiling height.
  3. 3Enter the number of doors and windows.
  4. 4View total wall area and sheets needed in both 4×8 and 4×12 sizes.

Formula Explanation

Drywall quantity is based on total wall area minus openings (doors and windows), divided by the sheet area. Standard door opening is 21 sq ft and window opening is 15 sq ft.

Wall Area = Perimeter × Height Net Area = Wall Area − (Doors × 21) − (Windows × 15) 4×8 Sheets = Net Area ÷ 32 4×12 Sheets = Net Area ÷ 48

Variables:

Perimeter2 × (length + width) in feet
21 sq ftAverage door opening size
15 sq ftAverage window opening size

Worked Examples

12×12 room, 8ft ceiling, 1 door, 2 windows

  1. 1. Perimeter = 2 × (12+12) = 48 ft
  2. 2. Wall area = 48 × 8 = 384 sq ft
  3. 3. Net = 384 − 21 − 30 = 333 sq ft
  4. 4. Sheets (4×8) = 333 / 32 = 11 sheets
Result: 11 sheets of 4×8 drywall (12 with waste allowance)

Why Use This Calculator

  • Accurate material estimates save money and reduce waste.
  • Accounts for doors and windows automatically.
  • Compares standard (4×8) and large-format (4×12) sheet options.
  • Includes waste allowance for a realistic purchase quantity.
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Tips & Best Practices

  • Use 4×12 sheets for 8-foot ceilings to minimize seams.
  • Add 10–15% for waste, cuts, and mistakes.
  • Use moisture-resistant drywall in bathrooms and kitchens.
  • Buy a few extra sheets — drywall is inexpensive and damages easily.

Common Mistakes to Avoid

❌ Forgetting to subtract doors and windows from total area.

✅ This calculator does it for you — enter the correct count of openings.

❌ Not buying enough extra for cuts and waste.

✅ Add at least 10% to the calculated number. Drywall is cheap; running short is costly.

❌ Using standard drywall in wet areas like bathrooms.

✅ Use green board (moisture-resistant) or cement board in bathrooms and around tubs.

Frequently Asked Questions

What size drywall should I use?
4×8 is the most common and easiest to handle. 4×12 sheets reduce seams in rooms with 8-foot ceilings. Use 1/2-inch thickness for walls and 5/8-inch for ceilings or soundproofing.
How do I calculate drywall for ceilings?
Multiply room length by width for ceiling area. This calculator estimates walls only. For ceilings, divide ceiling area by 32 (4×8 sheets) or 48 (4×12 sheets) and add to your wall estimate.
How many screws do I need per sheet?
Plan for about 28–32 screws per 4×8 sheet. Screws should be placed every 12 inches on edges and every 16 inches in the field (center area).
Should I install drywall horizontally or vertically?
Horizontally is standard for walls. It reduces the linear footage of seams and aligns better with stud spacing. Vertical installation is used for shorter walls or specific design requirements.
How much does drywall cost per sheet?
Standard 4×8 drywall costs $10–15 per sheet. Moisture-resistant runs $12–18, and fire-rated about $14–20. Prices vary by region and thickness.
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Disclaimer: This calculator is provided for informational and educational purposes only. Results are estimates and should not be used as a substitute for professional advice. RediCalc.com makes no guarantees regarding the accuracy, completeness, or suitability of any calculations. Always consult a qualified professional before making financial, health, construction, or other important decisions.

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