Primer calculator — square feet & US gallons

Keep primer separate from your finishing paint

Use only the surfaces that will actually be primed. Apply the primer’s own coverage and number of coats. Spot priming can be entered as a measured area; whole-room priming uses the full selected surface area.

For example, 300 sq ft at 300 sq ft per gallon and one coat needs one US gallon. Porosity, stains, preparation and the current coating instructions determine the actual process.

Does “paint + primer” remove this step?

A product name alone does not establish whether your surface needs a separate primer. Read the preparation guidance for both coatings. The calculator does not approve a primer/topcoat pairing.

Primer for a 10 × 10 or 12 × 12 ft room

With eight-foot walls and 20 sq ft of door/window openings, a 10 × 10 ft room has 300 sq ft of paintable walls; a 12 × 12 ft room has 364 sq ft. At an illustrative 300 sq ft per US gallon and one coat, they need 1 and about 1.213 US gallons respectively. If the chosen primer is sold only in one- and five-gallon containers, that means one or two one-gallon containers before extra allowance. These examples exclude the ceiling.

Coverage and coats change the result

Manufacturer ranges use their lower coverage value by default. A quoted “up to” coverage is not a guarantee on every surface. Check porosity, colour change, application method and preparation; adjust the form to your current label.