Paint Calculator

Estimate paint gallons from wall area, number of coats, and coverage per gallon.

Calculator

Estimate paint quantity

Enter paintable wall area, coats, and coverage to estimate gallons needed for a room or project.

Wall area (sq ft)CoatsCoverage (sq ft / gal)

Paintable area

800 sq ft

Paint needed

2.29 gal

Gallons to buy

3 gal

Formula assumptions

Paintable area equals wall area x number of coats.
Default coverage is 350 square feet per gallon.
Gallons to buy rounds up to the next whole gallon.
Doors, windows, texture, primer, and color changes can affect real paint use.

Planning summary

Paint estimate Wall area: 400 sq ft Coats: 2 Coverage: 350 sq ft per gallon Paint needed: 2.29 gallons Gallons to buy: 3 Formula: wall area x coats, divided by coverage per gallon.

Share links keep the current inputs so you can return to this estimate later.

Estimates are for planning only. Check local prices, site conditions, product labels, and applicable rules before buying materials or building.

Explanation

How paint quantity is calculated

How the calculation works

The calculator multiplies paintable wall area by the number of coats, then divides by the selected coverage per gallon. Gallons to buy are rounded up.

Example calculation

For 400 square feet of wall area with two coats at 350 square feet per gallon, the estimate is 2.29 gallons, so plan to buy 3 gallons.

Before you buy

Turn gallons into a practical paint shopping plan.

A gallon estimate is the starting point. Primer, paint type, surface condition, tools, and room details can all change what belongs in the cart.

Check whether primer belongs in the estimate

Primer can change both the shopping list and the final finish, especially on patches, stains, bare drywall, or strong color changes.

Read guide

Choose the right paint type before comparing gallons

Interior and exterior paint are built for different conditions, so match the product to the surface before relying on coverage numbers.

Read guide

Build the full materials list

Rollers, brushes, tape, trays, drop cloths, patching supplies, and cleanup items often matter as much as the paint itself.

Read guide

Use product coverage carefully

Coverage per gallon changes with texture, sheen, color change, primer, and wall condition.

Read guide

Materials checklist

Paint project shopping checklist

Use the gallon estimate as the starting point, then confirm prep supplies, tools, and finish details before buying.

BuildMetric may add affiliate links here later. Recommendations should stay practical, clearly disclosed, and tied to the project estimate.Read the affiliate disclosure.

Interior or exterior paint

Match the product to the room, surface, sheen, and cleaning needs.

Primer

Useful for bare drywall, stains, patches, and strong color changes.

Rollers and brushes

Choose roller nap by wall texture and keep an angled brush for edges.

Tape, trays, and drop cloths

Prep supplies usually decide whether the job feels clean or chaotic.

Patching and sanding supplies

Fill holes, sand rough areas, and clean surfaces before painting.

Before buying

Check the coverage range on the exact paint label.
Estimate primer separately from finish paint.
Keep color name, sheen, and room label for touch-ups.

FAQ

Paint calculator questions

How do I calculate paint needed?

Multiply paintable wall area by the number of coats, then divide by coverage per gallon.

How much area does one gallon of paint cover?

Many paints cover about 300 to 400 square feet per gallon, but always check the product label.

Should I include windows and doors?

For a rough estimate, you can use total wall area. For a tighter estimate, subtract large windows and doors.

Do I need primer?

Primer may be needed for bare drywall, stains, strong color changes, or uneven surfaces. It can change material needs.

Formula and assumptions

How this estimate should be used

Estimating paint gallons for rooms, walls, touch-ups, and simple homeowner painting projects.

Formula summary

Paint needed = paintable area x number of coats / coverage per gallon
Gallons to buy are rounded up to the next whole gallon
Large openings can be subtracted for a tighter estimate

Planning assumptions

Coverage varies by paint product, wall texture, primer, color change, and application method.
Primer should be estimated separately when needed.
The calculator is for planning gallons, not choosing a paint system.

Next steps

Turn the estimate into a plan.

Use the result as a starting point, then check the supporting guide or continue with the next calculator before buying materials.

Paint Tools and Materials Checklist

Plan the paint, primer, rollers, brushes, tape, drop cloths, trays, patching supplies, and cleanup items for a room project.

Open guide

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