Paint Calculator
Estimate paint gallons needed for walls, ceilings, and trim
Length of the room
Width of the room
Height of walls
Standard door: 20 sq ft
Standard window: 15 sq ft
Most projects need 2 coats
Wall Area
—
sq ft
Paintable Area
—
sq ft
Paint Needed
—
gallons
Estimated Cost
—
USD
Disclaimer: Results are estimates based on standard formulas. Not a substitute for professional advice from a licensed contractor, engineer, or architect. Verify all calculations before making purchasing or construction decisions.
How to Use This Calculator
Buying the right amount of paint saves you time and money. Our paint calculator accounts for room dimensions, doors, windows, and number of coats.
- Measure room length, width, and ceiling height
- Count the number of doors and windows
- Decide how many coats you will apply
- Enter your measurements in the calculator
- Buy 10% extra for touch-ups
Expert Insights
Smart analysis for your Painting project
Paint Quality ROI
Premium paint ($50+/gal) covers 20-30% more area per gallon and lasts 7-10 years vs 3-5 for budget. AI calculates true cost-per-year.
Primer Optimization
Painting over dark colors or bare drywall? AI recommends primer to save up to one full coat of paint — cutting project cost by 20-30%.
Labor vs DIY Comparison
Professional painters average 2-3x faster. AI compares your room size against national labor rates for an accurate DIY savings estimate.
Calculation Formula
Wall area = 2 x (L + W) x H
Paintable = Wall area - (Doors x 20) - (Windows x 15)
Gallons = (Paintable x Coats) / 350
Paint Quality Comparison
| Quality Tier | Price/Gallon | Coverage/Gallon | Lifespan | Best For |
|---|---|---|---|---|
| Economy | $15-25 | 250-300 sq ft | 2-4 years | Rental touch-ups |
| Standard | $30-45 | 300-400 sq ft | 5-7 years | Most interior walls |
| Premium | $50-80 | 350-450 sq ft | 7-10+ years | High-traffic, exteriors |
Authority References
Our calculations are based on guidelines and standards from these authoritative sources:
- Paint Quality Institute — Coverage Rates & Application Guidelines. Learn more
- Sherwin-Williams — Paint Calculator & Coverage Charts. Learn more
- Benjamin Moore — Painting Best Practices Guide. Learn more
Frequently Asked Questions
How much does a gallon of paint cover?
One gallon of interior paint typically covers 350-400 square feet with one coat.
How many coats of paint do I need?
Most projects require 2 coats. You may need 3 when painting over dark colors or on bare drywall without primer.