Paint Coverage Calculator Formula
Understand the math behind the paint coverage calculator. Each variable explained with a worked example.
Formulas Used
Total Coverage Needed
total_coverage_needed = area * num_coatsGallons Needed
gallons = ceil(area * num_coats / coverage_rate)Or in Quarts
quarts = ceil(area * num_coats / coverage_rate * 4)Variables
| Variable | Description | Default |
|---|---|---|
area | Paintable Area(sq ft) | 400 |
coverage_rate | Coverage Rate(sq ft/gallon) | 350 |
num_coats | Number of Coats | 2 |
How It Works
How to Calculate Paint Coverage
Formula
Gallons = (Area × Number of Coats) / Coverage Rate
Standard interior latex paint covers approximately 350-400 sq ft per gallon. Factors that reduce coverage include rough or textured surfaces, porous substrates, and dark-to-light color changes.
Worked Example
Painting 400 sq ft of wall area with 2 coats at 350 sq ft/gallon.
- 01Total coverage = 400 × 2 = 800 sq ft
- 02Gallons = 800 / 350 = 2.29 → 3 gallons
Frequently Asked Questions
How much wall does a gallon of paint cover?
A gallon of standard interior latex paint covers 350-400 square feet on smooth surfaces. Textured or porous surfaces may reduce coverage to 250-300 sq ft per gallon.
Do I always need two coats?
Two coats is recommended for most situations, especially when changing colors. One coat may suffice when repainting the same or very similar color with high-quality paint.
How do I account for doors and windows?
Subtract approximately 21 sq ft per standard door and 15 sq ft per standard window from your total wall area. Use the Paint Gallons Calculator for automatic deductions.
Learn More
Guide
How to Estimate Paint Needed for Interior and Exterior Projects
Learn how to calculate the amount of paint needed for walls, ceilings, trim, and exteriors. Covers coverage rates, surface types, primer needs, and multi-coat calculations.
Ready to run the numbers?
Open Paint Coverage Calculator