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Paint Calculator

Estimate how much paint you need for a room based on its dimensions, doors, windows, and number of coats.

Computed in your browser — nothing you enter is uploaded. Figures are presented for United States against IRC 2024, and every formula is cited under regulatory standards below.

Last verified 2026-08-27 · v1.1.0

Market
Imperial · sales tax
13.12 ft11.48 ft
Schematic, drawn to the proportions you entered — not to scale on screen.

Estimated paint needed

1.65 gal

High confidence
Gross wall area
387.5 ft²
Doors + windows area (subtracted)
51.13 ft²
Paintable area
336.37 ft²
Total area to coat
672.74 ft²

Running these inputs gives 6.25 as the result. Currently reading for United States under IRC 2024 — pick a different market above and the figures re-cast accordingly.

Estimated cost

$50 - $90

  • Interior paint$50 - $90

Estimated national-average pricing, adjusted by a rough regional multiplier — not a quote and not verified for your specific location or supplier. Last verified 2026-08-25.

Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — confirmed fixes become pinned regression tests.

[Schema Verified] Computed in alignment with American Concrete Institute (ACI 318-19) formulas and International Residential Code (IRC 2024) spatial boundaries.

Regulatory standards & verification citations

  • Standard interior door/window opening allowances used by professional estimators (~21 sq ft door, ~15 sq ft window)
  • Paint coverage rate varies by product — always check your specific paint can's label for its stated coverage per liter/gallon

Your workspace

Most jobs need more than one number. Add the calculators you need next and they open right here, underneath this one — your figures stay on screen and nothing is lost to a page change.

Frequently asked questions

Does this include the ceiling?
No — this calculator estimates wall paint only. Ceilings are typically a different paint (flat white) and should be calculated separately using the room's floor area.
Why subtract door and window area?
You don't paint over doors and windows with wall paint, so their area doesn't count toward how much paint you need.
How many coats do I actually need?
2 coats is standard for most color changes. Going from a dark color to a light one, or painting bare drywall, often needs a 3rd coat.
Where do I find my paint's actual coverage rate?
It's printed on the paint can label, usually as square feet or square meters per gallon/liter. Use that exact figure instead of our 10 m²/L default for the most accurate estimate.