Paint Coverage Calculator Guide: Wall Area to Gallons

Use known wall area, coats, coverage rate, and waste percentage to estimate gallons of paint needed.

Use the Paint Coverage Calculator when you already measured the surface area and want a direct gallon estimate.

Coverage depends on surface condition

Paint cans usually list coverage per gallon, but rough, porous, dark, damaged, or heavily patched walls can need more paint.

Why waste margin matters

A small waste percentage covers roller loss, touch-ups, surface variation, and measurement errors. For repainting similar colors, 5–10% may be enough. For rough walls, use more.

Before buying

• Check whether primer is needed.
• Confirm if one or two coats are realistic.
• Keep a little extra paint for future touch-ups.