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Interior Paint Calculator — Room Gallons

Paintable sq ft = walls + ceiling − openings; gallons = sq ft × coats ÷ coverage.

Interior paint gallons for walls and ceiling. Planning estimates only — verify measurements and local codes on site.

Inputs

450
450
712
0500
14
250500

Smart analysis

Recommendations

Tailored to your live inputs and result—guidance only, not professional advice.

  • Round up

    Buy a little extra for real-world waste

    Measurements are ideal—paint, flooring, and food projects usually need a small overage for cuts, mistakes, and touch-ups.

Scenario studio

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Scenario B

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Plain-English guide

Terms & how it works

Confused by a field? Read the short definitions here while you use the tool.

  • Room length (ft)

    The “Room length (ft)” value used in this tool’s formula. Adjust it to see results update live.

  • Room width (ft)

    The “Room width (ft)” value used in this tool’s formula. Adjust it to see results update live.

  • Ceiling height (ft)

    The “Ceiling height (ft)” value used in this tool’s formula. Adjust it to see results update live.

  • Openings (sq ft)

    The “Openings (sq ft)” value used in this tool’s formula. Adjust it to see results update live.

  • Coats

    The “Coats” value used in this tool’s formula. Adjust it to see results update live.

  • Coverage (sq ft/gal)

    The “Coverage (sq ft/gal)” value used in this tool’s formula. Adjust it to see results update live.

How this calculator works

Interior paint gallons for walls and ceiling. Planning estimates only — verify measurements and local codes on site. Paintable sq ft = walls + ceiling − openings; gallons = sq ft × coats ÷ coverage. Example: 12×14×8 room, 2 coats, 400 sq ft/gal → ~3–4 gallons walls+ceiling.

Paintable sq ft = walls + ceiling − openings; gallons = sq ft × coats ÷ coverage.

Example: 12×14×8 room, 2 coats, 400 sq ft/gal → ~3–4 gallons walls+ceiling.

When to use this Interior Paint Room

Common use cases

  • Interior paint gallons for walls and ceiling.
  • Sanity-check with this case: 12×14×8 room, 2 coats, 400 sq ft/gal → ~3–4 gallons walls+ceiling.
  • The relationship is: Paintable sq ft = walls + ceiling − openings; gallons = sq ft × coats ÷ coverage.

Localized examples

  • Construction & Bidding: the example on this page uses the same formula as the widget.

What you get

  • Fields: Room length (ft), Room width (ft), Ceiling height (ft), Openings (sq ft)
  • Paintable sq ft = walls + ceiling − openings; gallons = sq ft × coats ÷ coverage.
  • Example on the page: 12×14×8 room, 2 coats, 400 sq ft/gal → ~3–4 gallons walls+ceiling.

How to Calculate Interior Paint Room Step-by-Step

  1. 1Enter Room length (ft), Room width (ft), Ceiling height (ft), then the remaining fields. Use the values you have, not a catalog average, unless that is all you know.
  2. 2Paintable sq ft = walls + ceiling − openings; gallons = sq ft × coats ÷ coverage.
  3. 3Worked case: 12×14×8 room, 2 coats, 400 sq ft/gal → ~3–4 gallons walls+ceiling.
  4. 4Buy materials after you walk the job. This is a first-pass quantity, not a purchase order.

Governing formula

Paintable sq ft = walls + ceiling − openings; gallons = sq ft × coats ÷ coverage.

12×14×8 room, 2 coats, 400 sq ft/gal → ~3–4 gallons walls+ceiling.

Example: set Room length (ft) = 12, Room width (ft) = 14, Ceiling height (ft) = 8, then read the result.

Variable definitions

  • roomLengthFt

    Room length (ft)

    The “Room length (ft)” field. Default 12; typical range 4–50.

  • roomWidthFt

    Room width (ft)

    The “Room width (ft)” field. Default 14; typical range 4–50.

  • roomHeightFt

    Ceiling height (ft)

    The “Ceiling height (ft)” field. Default 8; typical range 7–12.

  • openingsSqFt

    Openings (sq ft)

    The “Openings (sq ft)” field. Default 60; typical range 0–500.

  • coats

    Coats

    The “Coats” field. Default 2; typical range 1–4.

  • coveragePerGal

    Coverage (sq ft/gal)

    The “Coverage (sq ft/gal)” field. Default 400; typical range 250–500.

  • The takeoff (Paintable sq ft = walls + ceiling − openings; gallons = sq ft × coats ÷ coverage.) ignores waste, code, and what you find when you open the wall. Measure twice on site.
  • Nothing here is uploaded for the calculation itself.

Frequently Asked Questions

Paintable sq ft = walls + ceiling − openings; gallons = sq ft × coats ÷ coverage.

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Reviews & Ratings

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4.8

out of 5.0

4 reviews

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Your rating

Aisha K.

Mar 12, 2026

Clean layout and the results update instantly. Exactly what I needed for a quick planning check.

Daniel R.

Feb 28, 2026

Very usable on mobile. Would love a save/export option later, but the math feels solid.

Priya S.

Feb 3, 2026

The FAQ section answered my questions before I even had to search. Smooth dark mode too.

Marcus L.

Jan 19, 2026

Simple inputs, clear outputs. This replaced three bookmarks I used to juggle.

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