Painting

Paint Calculator for Room Walls

Estimate finish paint for rectangular room walls using coats, label coverage, openings, and waste. Optionally estimate primer separately using its own coats, coverage, and user-entered price.

Written by Arthur Weng Reviewed July 17, 2026 Sources

Painting

Calculator inputs

Room dimensions

Measure the room footprint and painted wall height.

Room widthftRoom lengthftWall heightft

Finish paint

Use the finish-paint coats and coverage from your plan and product label.

Number of coatsCoverage per gallonsq ft/gal

Purchase adjustments

Waste factor%Your finish paint price (optional)$/gal

Primer (optional)Estimate primer as a separate material line when you include it.

Include primerUse primer only as directed for your surface and product.

Door and window deductionsSubtract openings only when they remove a meaningful amount of paintable wall.

Doors to subtract (optional)Average door areasq ftUsed only when door count is greater than 0.Windows to subtract (optional)Average window areasq ftUsed only when window count is greater than 0.

Enter your own local prices or fees only if you want a cost estimate.

Calculated in your browser.Project dimensions stay on this device. Review the assumptions below before buying material.

Paint Calculator Results

Results update in your browser as you edit inputs. Use the shopping-list button for a printable project summary.

Enter project dimensions to calculate material quantity.

Detailed guide

Need the assumptions, examples, and troubleshooting?

The calculator stays focused here. The supporting reference has moved to its own page.

Read the Paint Calculator for Room Walls guide