Paint Calculator
Use your own numbers after reviewing the formula and worked example.
Quick answer
Paint quantity depends on paintable surface area, coat count and the product’s coverage per gallon.
Formula or method
Keep units, percentages and time periods consistent. The formula is useful as a transparent check on the calculator result and helps explain why changing one input changes the answer.
Step-by-step
- Calculate wall area.
- Subtract large openings if desired.
- Multiply by coat count.
- Divide by coverage and round up to practical container sizes.
Worked example
If paintable area is 1,000 sq ft and two coats are needed at 400 sq ft per gallon, the arithmetic estimate is 5 gallons.
How to interpret the result
Texture, primer, color changes and surface porosity can alter real coverage.
When the answer is used for a purchase, loan, payroll decision, construction order, school grade, health estimate or other real-world choice, verify the assumptions that matter in that context. Accurate arithmetic still depends on accurate inputs.
Common mistakes
- Using floor area instead of wall area.
- Forgetting multiple coats.
- Assuming all paints have identical coverage.
Frequently asked questions
Should primer be counted separately?
Yes if required.
Do I subtract windows?
You can subtract large openings for a tighter estimate.
Why round up?
Paint is sold in fixed container sizes and running short is inconvenient.