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/// Walls, ceilings & coats

Paint Calculator

Use the paint calculator to total selected wall and ceiling area, subtract openings, multiply by the entered coat count, add waste, and divide by coverage stated for the actual paint. The decimal gallon equivalent and rounded purchase quantity are shown separately. Surface condition, primer, color change, application loss, and package sizes require project review.

Content reviewed Jul 16, 2026 · Source records reviewed through Jul 15, 2026

01

Room surfaces and paint coverage

Enter the coverage stated for the exact paint and surface. Ceiling area is optional and large openings are subtracted from walls.

ftExample starting measurement — replace it with your field measurement.
ftExample starting measurement — replace it with your field measurement.
ftExample starting measurement — replace it with your field measurement.
ft²Example starting measurement — replace it with your field measurement.
Example starting value — replace it with the project or product value.
coatsRequired — enter a project-specific planning value and verify it before ordering. ProjectQty does not apply an unsupported default.Coats must be greater than zero.
ft²/galRequired — enter the value from the exact product label or current technical sheet. ProjectQty does not guess this value.Coverage must be greater than zero.
%Required — enter a project-specific planning value and verify it before ordering. ProjectQty does not apply an unsupported default.
USDOptional — enter your current local price per 1-gallon equivalent container.
View current estimate

/// Answer-first planning notes

How much paint follows from coated area, coats, and product coverage?

How much paint follows from coated area, coats, and product coverage checkpoints
Planning inputCalculation roleProduct check
Coated surfacesCreate net paintable areaChoose walls and ceiling deliberately
CoatsMultiply coverage demandFollow the coating system
Coverage per gallonConvert area into product volumeUse the exact selected paint data

/// Formula & field notes

How this paint estimate works

FormulaPaint volume = coated area × number of coats × (1 + waste %) ÷ stated product coverage per gallon or package.

Worked example

A 20 × 12 × 8 ft room, 20 ft² of openings, ceiling included, two coats, and 350 ft²/gal needs about 4.18 gal, planned as 5 whole gallons.

/// Source trail

Data & assumptions

Every source has a declared scope. A reference can support a conversion or product assumption without turning this estimate into a supplier quote.

National Institute of Standards and Technology · Primary evidenceNIST Guide to the SI, Appendix B: Conversion Factors

Exact international-foot to meter conversion; U.S. survey-foot conversion is explicitly outside this claim.

Effective 2025-08-18 · Reviewed 2026-07-15 · Next review 2027-07-15
NOAA National Geodetic Survey · Prequalified fallbackThe DSDATA Format, Appendix D: U.S. Survey Foot vs International Foot

Independent confirmation that one international foot equals exactly 0.3048 meters; U.S. survey-foot conversion remains distinct.

Effective 2025-06-10 · Reviewed 2026-07-15 · Next review 2027-07-15
National Institute of Standards and Technology · Primary evidenceNIST Handbook 44 (2026): exact U.S. liquid gallon definition

Exact U.S. liquid-gallon definition; Imperial and dry gallons are excluded.

Effective 2026-01-06 · Reviewed 2026-07-15 · Next review 2027-07-15
North Carolina General Assembly · Prequalified fallbackNorth Carolina General Statutes: U.S. liquid gallon definition

Independent statutory confirmation of the 231-cubic-inch U.S. liquid gallon.

Effective 2026-04-17 · Reviewed 2026-07-15 · Next review 2027-07-15

/// Common questions

Paint calculator FAQ

What should I verify before ordering paint?

Confirm field dimensions and label coverage, coats, surface condition, and application method against the exact product or supplier information. ProjectQty shows the assumptions so you can replace planning defaults before ordering gallons or explicitly labeled one-gallon equivalents.

How does waste affect the paint estimate?

Waste is applied after the base geometry is calculated and before discrete packages or pieces are rounded up. Use a higher allowance for complex layouts, cuts, pattern matching, breakage, or uncertain field dimensions.

Is this paint result a professional design?

No. It is a quantity-planning result. Surface preparation, lead-safe practices, ventilation, coating compatibility, and safety instructions remain the user's responsibility.

/// Keep planning

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