Home Renovation · Free calculator

Paint Calculator

Estimate wall paint from room dimensions, openings, coats and the coverage stated on your paint container.

Your project inputs

Prefilled measurements and product coverage are editable examples, not product or structural recommendations. All fields are required unless marked optional.

Measurement units

Changing units converts current measurements, product coverage and price per area. Results clear when any input changes.

Paint coverage / container volume unit

Estimate whole containers

Room length (m)

Measured dimension in the selected unit.

Room width (m)

Measured dimension in the selected unit.

Wall height (m)

Measured dimension in the selected unit.

Combined door/window area (m²) — optional

Enter a measured area in the displayed square unit. Blank openings = 0.

Number of coats

Whole coats; zero represents no paint application.

Paint coverage (m² per L)

Use product coverage for one coat. Greater than zero; surface absorption affects actual coverage.

Waste allowance (%) — optional

Optional extra material added to the estimate. Blank or 0 means no allowance.

Container volume (L)

Purchasable volume per container, greater than zero.

Your estimate

Materials & purchasing quantities

Review the example values, enter your measurements and product specifications, then calculate. Results clear whenever inputs change.

How much paint do I need for a room?

Gross wall area = 2 × (room length + room width) × wall height. Paintable area = gross area − combined opening area. Coat area = paintable area × coats. Coverage requirement = coat area × (1 + waste/100). Paint volume = coverage requirement ÷ coverage per liter or gallon. Containers round upward.

Worked example

A 4 m × 3 m room with 2.5 m walls has 35 m² of wall area. Subtract 3 m² of openings: 32 m². Two coats need 64 m² of coverage; 10% extra gives 70.4 m². At 10 m²/L, that is 7.04 L, or three 2.5 L containers.

Unit conversions

1 ft = 0.3048 m; 1 in = 0.0254 m; 1 cm = 0.01 m. Area conversions use squared length factors, and volume conversions use cubed factors. 1 yd³ = 27 ft³ = 0.764554857984 m³; 1 L = 0.001 m³.

Assumptions & limitations

Assumes four rectangular walls of equal height. Ceilings, trim, alcoves and additional surfaces are not included. Enter measured door/window areas; openings cannot exceed total wall area.
Manufacturer coverage depends on substrate, surface absorption, texture, application method, primer and coat thickness. Use coverage appropriate to your surface; extra coats or primer may be needed.
Waste is extra coverage added to the estimate. US liquid gallons (3.785411784 L) and Imperial gallons (4.54609 L) differ; choose the one on your product label. Zero coats represents no paint application.