📖 Overview
Enter your room size and coverage rate to estimate the gallons of paint needed for your project.
⚙️ How It Works
Calculates total paintable wall area from room dimensions, then divides by the coverage rate per gallon to determine how much paint to buy.
The Formula
Wall Area = 2 × (Length + Width) × Height | Gallons = Wall Area ÷ Coverage per Gallon
| Length, Width | Room floor dimensions in feet |
| Height | Ceiling height in feet (US standard: 8–9 ft) |
| Coverage | Sq ft per gallon (350 for smooth walls; 250–300 for textured) |
💡This formula calculates all four walls but does NOT subtract windows and doors. A rough rule of thumb: subtract 20 sq ft per standard door and 15 sq ft per window. For two coats, double your gallon estimate.
Quick Reference
| Room size | Wall area (8 ft ceiling) | Gallons needed (350 sq ft/gal) |
|---|---|---|
| 10 × 10 | 320 sq ft | ~0.9 gal |
| 12 × 12 | 384 sq ft | ~1.1 gal |
| 14 × 16 | 480 sq ft | ~1.4 gal |
| 20 × 20 | 640 sq ft | ~1.8 gal |
Practical Tips
💡 Add 10–15% extra for touch-ups and wastage.
💡 Textured or rough surfaces absorb more paint — use 250 sq ft/gallon instead of 350.
💡 Two coats nearly always look better; plan for double the quantity.
💡 Measure twice — a 12×14 room has 40% more wall area than a 10×10.
Frequently Asked Questions
❓ Does this include the ceiling?
No. The formula covers the four walls only. Add ceiling area (length × width) separately.
❓ What coverage rate should I use?
350 sq ft/gal for smooth drywall, 250–300 for textured or previously unprimed surfaces.