Room Paint Quantity Calculator
Use our free online Paint Calculator to perform fast, accurate calculations with instant formulas, step-by-step arithmetic, and verified reference benchmarks.
Paint Calculator
Instant Live Computation • Zero Waiting
Adjust inputs on the left for instantaneous live computation.
How to Calculate: The Paint Calculator Formula
Industry standard: One gallon of paint covers approximately 350 to 400 square feet of smooth wall surface per coat.
Step-by-Step Calculation Guide
- Input room length, width, and ceiling height.
- Enter number of standard doors (approx 20 sq ft each) and windows (approx 15 sq ft each).
- Select number of paint coats (2 coats recommended for rich coverage).
- Review total paint gallons and quarts to purchase.
Practical Paint Calculator Examples
Perimeter = 2(12 + 15) = 54 ft. Gross wall area = 54 × 8 = 432 sq ft. 2 doors (40 sq ft) + 2 windows (30 sq ft) deducted. Net = 362 sq ft. 2 coats.
Wall: 10 ft wide by 8 ft high = 80 sq ft. 2 coats = 160 sq ft.
Standard Paint Coverage and Volume Standards
Official reference values and benchmark classifications based on standard institutional guidelines.
| Paint Container Size | Average Coverage (1 Coat) | Average Coverage (2 Coats) | Typical Room Size |
|---|---|---|---|
| 1 Quart (32 oz) | 85 – 100 sq ft | 45 – 50 sq ft | Accent wall, small powder room |
| 1 Gallon (128 oz) | 350 – 400 sq ft | 175 – 200 sq ft | Small bedroom or home office |
| 2 Gallons | 700 – 800 sq ft | 350 – 400 sq ft | Standard master bedroom or living room |
| 5-Gallon Bucket | 1,750 – 2,000 sq ft | 875 – 1,000 sq ft | Entire apartment or open-concept floor |
Frequently Asked Questions about Paint Calculator
How many coats of paint are usually required?
Two coats are recommended for optimal color depth, durability, and uniform sheen, especially when changing colors or painting over bare drywall primer.
How much wall area do doors and windows take up?
Standard interior doors subtract roughly 20 to 21 square feet. Standard residential windows subtract roughly 12 to 15 square feet.
Do textured walls require more paint?
Yes. Heavy plaster or rough stucco surfaces can absorb up to 20% to 30% more paint than smooth drywall, lowering coverage to 250-300 sq ft per gallon.
Is primer necessary before painting?
Primer is necessary when painting bare drywall, unpainted wood, transitioning from oil to latex, or making dramatic color shifts (e.g. dark navy to white).