construction ToolUpdated 2026-09-19
Paint Calculator
Estimate how many gallons of paint you need to buy for room walls and ceilings based on dimensions and number of coats.
Construction & Material Estimate Notice: Material quantity calculations are theoretical estimates. Actual requirements depend on sub-base conditions, irregular surface cuts, and structural engineering specifications. Always verify with your supplier or licensed contractor prior to ordering.
Formula & Mathematical Methodology
Gallons = (Total Wall Area × Coats) ÷ 350 sq ft/gal
Calculates total wall surface area, multiplies by coats, and divides by the standard 350 sq ft coverage per gallon.
How to Use This Paint Calculator
- Enter total room perimeter, ceiling height, and number of coats.
Step-by-Step Worked Example
Scenario: 50 ft perimeter, 9 ft height, 2 coats
1. Wall area: 50 × 9 = 450 sq ft
2. Two coats: 450 × 2 = 900 sq ft
3. Gallons needed: 900 ÷ 350 = 2.57 gallons (buy 3 gallons)
Final Calculated Result: 2.57 Gallons (Buy 3 Gallons)
What Does Your Result Mean?
One standard gallon covers approximately 350 to 400 square feet of smooth interior drywall.
Common Practical Applications:
- Interior bedroom and living room painting
- Exterior siding painting
Important Limitations & Assumptions:
- Textured walls or unprimed fresh drywall absorb more paint, reducing coverage to approx 250-300 sq ft/gal.
Frequently Asked Questions
How much area does one gallon of paint cover?
One gallon of quality interior latex paint covers approximately 350 to 400 square feet on prepared walls.
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