Should primer be included as another coat?

Calculate primer separately using the primer label's coverage. Primer and finish paint often have different spread rates.

Should I subtract doors and windows?

Subtract their combined area for a closer estimate. For a small project, leaving minor openings included can also serve as a practical buffer.

Why is the coverage rate editable?

Coverage varies by product, surface texture, porosity, color change and application. The number printed on the selected product is more reliable than a universal default.

Does the result include two coats?

It includes the exact number of coats entered. The calculator multiplies paintable surface area by that number before dividing by coverage.

Home project calculator

Paint Calculator

Estimate interior paint from room dimensions, excluded doors and windows, coats, ceiling area and the coverage printed on the paint label.

Live estimate

Enter project measurements

Room lengthftRoom widthftWall heightftDoors + windowsft²Number of coatscoatsLabel coverageft²/galOptional allowance%Include ceiling

Estimated paint

1.81 gal

Plan on 2 whole gallons if buying gallon cans only.

Paintable area: 316 ft²
Area across all coats: 632 ft²
Wall area: 352 ft²
Liters: 6.84 L

Transparent calculation

Formula used

Gallons = paintable area × coats ÷ coverage per gallon

Wall area is 2 × (length + width) × height. Door and window area is subtracted once, then coats and any optional allowance are applied.

Worked example

A 12 × 10 × 8 ft room has 352 ft² of wall area. After excluding 36 ft², two coats cover 632 ft²; at 350 ft² per gallon, the estimate is about 1.81 gallons.

How to use this estimate

1Measure the room length, width and wall height.
2Add the combined area of doors, windows or surfaces not being painted.
3Select the number of coats and include the ceiling only when needed.
4Replace the default coverage with the product label's spread rate.

Paint Calculator FAQs

Answers to the most common measurement and ordering questions.