How much does a gallon of paint cover?

Most interior paints cover 350–400 square feet per gallon on a smooth, primed surface in a single coat.

Prime new drywall, bare wood, patched areas and dramatic color changes. Over similar existing colors, a quality paint-and-primer often skips it.

Materials

Paint Calculator

Calculate gallons of paint and primer for walls, ceilings and trim.

100% free to useNo sign-up requiredImperial & metric units

How much paint do I need?

To find how much paint you need, multiply the paintable wall area by the number of coats and divide by the coverage rate, usually 350 to 400 square feet per gallon. A room with 60 ft of wall at 9 ft high needs about 3 gallons for two coats. Prime new drywall and big color changes first.

Inputs

Total wall lengthft

Add up the length of every wall you are painting.

Ceiling heightft

Coatscount

Coverage per gallonsq ft

Doors & windows to deductcount

Add primer coat

Waste allowanceApplied to material quantities

Results

Paint

2.86 gal

Round up to the nearest gallon

Paintable Area

500 sq ft

Primer

0 gal

Quarts (alt)

12 qt

Estimates update instantly as you type. Confirm against local code before ordering materials.

Running out of paint means a touch-up batch that never quite matches, while overbuying wastes money on cans you will never open. This free paint calculator estimates the exact gallons of paint and primer for any room from the wall length, ceiling height, number of coats, and your product coverage rate.

Coverage is not a fixed number. A smooth, primed wall stretches a gallon to 400 square feet, while porous drywall, textured surfaces, or a dramatic color change can pull that down sharply. Deduct doors and windows, account for primer where the surface needs it, and the estimate lands close to what you actually roll on.

How paint coverage is calculated

Paintable wall area is multiplied by the number of coats, then divided by the spread rate of a gallon. Openings are deducted and primer is estimated separately for new or patched surfaces.

Gallons = (Wall Area ft² × Coats) ÷ Coverage per Gallon

Paint coverage by surface

Approximate square feet covered per gallon, single coat.

Surface	Coverage per gallon	Notes
Smooth, primed wall	350 to 400 sq ft	Best-case spread rate
New or porous drywall	250 to 300 sq ft	Prime first for even coverage
Textured or rough	200 to 250 sq ft	Texture increases surface area

Most colors need two coats. A second coat uses slightly less paint than the first.

How to use it

1Enter the total wall length (perimeter) and ceiling height.
2Set the number of coats and your paint coverage rate.
3Read the gallons of paint and primer needed instantly.
4Round up to the nearest gallon or quart when buying.

Key terms explained

Spread rate: How far one gallon goes, typically 350 to 400 square feet per coat on a sealed surface.
Coat: One full application of paint. Most colors need two for even, durable coverage.
Primer: A base coat that seals porous surfaces and blocks old colors so the topcoat covers evenly.
Cut-in: Brushing paint along edges and corners a roller cannot reach. It uses a small share of each gallon.

Worked examples

Living room, two coats

A room with 60 ft of wall at 9 ft high needs about 3 gallons for two coats at 350 sq ft per gallon.

Single accent wall

A 14 ft × 9 ft accent wall takes roughly 1 gallon for two solid coats.

Pro tips from the field

1Always prime new drywall and patched areas; bare joint compound soaks up topcoat unevenly.
2A second coat uses slightly less paint than the first, so do not double your single-coat figure exactly.
3Dark and saturated colors often need an extra coat to hide; budget for it up front.
4Buy all your paint in one batch and box it together so the color is consistent wall to wall.

Common mistakes

Using the listed coverage rate on porous or dark surfaces that drink paint.
Skipping primer on new drywall or over big color changes.
Forgetting that a second coat uses a little less than the first.

Where it gets used

Interior repaints

Size paint and primer for a full room refresh in one estimate.

Accent walls

Quickly figure a single gallon or quart for a feature wall.

Whole-home projects

Total multiple rooms to order paint in one consistent batch.

Frequently asked questions

Free Paint Calculator for Walls & Ceilings

Buying too little paint means a mismatched touch-up batch; buying too much wastes money. This free paint calculator estimates the exact gallons of paint and primer for any room based on wall area, coats and your product coverage rate.

Adjust the spread rate for textured, porous or dark surfaces, and account for primer on new drywall or big color changes so your first coat lays down evenly.