Drywall Calculator

Plan for approximately one gallon (3.8L) of pre-mixed joint compound per 100 sq ft (9.3 m²), or one 4.5-gallon (17L) bucket per 15-20 sheets. Three coats are standard: tape coat, filler coat, and finish coat. Textured ceilings need more. Beginners typically use more than professionals due to sanding mistakes. Powder compound is more economical for large projects but requires mixing. Keep 10-15% extra for touch-ups.

Use approximately 32 screws per 4×8 sheet and 48 per 4×12 sheet on studs 16 inches (400mm) on center. Space screws 12 inches (300mm) apart along edges and 16 inches (400mm) in the field. Ceilings need closer spacing: 8 inches (200mm) apart. Use 1-1/4" (32mm) screws for 1/2" (12.5mm) drywall, 1-5/8" (41mm) for 5/8" (16mm). Sink screws slightly below surface without breaking paper.

Longer 4×12 sheets reduce joints and finishing time—ideal for ceilings and long walls. However, they're heavier (about 25% more), harder to maneuver, and may require two people. Standard 4×8 sheets are easier for DIY projects and tight spaces. For 8-foot (2.4m) ceilings, horizontal installation of 4×12 sheets can eliminate mid-wall joints entirely. Consider access to rooms—large sheets may not fit through doorways.

Drywall sheet prices vary: USA $10-18 per 4×8 sheet; Canada C$12-22; UK £8-15 per 2.4×1.2m; EU €8-18; Australia A$15-30. Moisture-resistant (green board) costs 20-30% more; fire-rated (Type X) 30-50% more. Installation typically costs 50-100% of material cost. Bulk orders (50+ sheets) often get discounts. Consider delivery fees for large orders—drywall is heavy and fragile.

Standard 1/2" (12.5mm) works for most walls and ceilings on 16" (400mm) stud spacing. Use 5/8" (16mm) for: ceilings on 24" (600mm) spacing (reduces sag), garage walls (fire code), and sound barriers. Use 1/4" (6mm) for curved walls and covering old surfaces. Moisture-resistant (green/blue board) for bathrooms. Cement board for tile backing in wet areas. Check local building codes for fire-rated requirements.

Calculate each room's wall area (2 × (length + width) × height) plus ceiling (length × width). Subtract door openings (20 sq ft/1.9 m² each) and windows (15 sq ft/1.4 m² each). Add all rooms together, divide by sheet size, and round up. Add 10-15% for waste and cutting. For complex layouts with many angles, add extra waste allowance. Order all at once for consistent lot matching and bulk pricing.