Paint Color Coverage Calculator
The paint bill before the tape — what the walls actually take at your coverage and coat count, and the gallon to buy.
Paint Color Coverage Calculator
Results recalculate instantly on every keystroke. Nothing you type is transmitted.
What this result does not account for
- Results are a model, not a quotation — an institution's own figures govern.
- Every input is an assumption; change one and the answer changes with it.
- Rounding is applied only at the display layer, so totals may differ by a cent from a statement that rounds each line.
In short: Two coats over 800 sq ft of wall puts 1,600 sq ft through the can; at 350 sq ft a gallon that is 4.57 gallons — buy 5. One coat alone would take 2.29, which is the part people forget: coats multiply the job, they do not add to it. Coverage of 300-400 sq ft a gallon covers most interior paints; the can's own number wins any argument.
Formula
gallons = (area − openings) × coats ÷ coverage; buy = ceiling of gallons
Coverage arithmetic is one division wearing a drop cloth: the wall area minus what the openings excuse, times the coat count, divided by the square feet a gallon honestly covers. Two is the default coat count because one-coat color is mostly marketing — the second coat is what makes the color even. Round the purchase up to the whole gallon: cut-in waste and a leftover can for touch-ups are cheaper than a second run to the store. The construction side keeps a contractor-grade paint calculator for bigger jobs.
Worked Example
- Enter the wall area and what the openings excuse.
- Set the coats and the can's coverage.
- Buy the rounded gallon and keep the receipt.
Defaults: (800 − 0) × 2 = 1,600 sq ft ÷ 350 = 4.57 gallons — buy 5; one coat would take 2.29.
Strengths & Limits Of This Model
Where this engine is strong
- Runs entirely in your browser — no figure you type is transmitted or stored.
- Shows the full working, so every number can be traced and challenged.
- Free, unmetered and free of affiliate incentives.
Where it stops
- Generalised assumptions cannot capture every individual circumstance.
- Jurisdiction-specific rules and mid-year changes may not be reflected.
- A model output is not a substitute for a professional review of your position.
Practical Use Cases
Bedroom refresh
the two-coat standard
Accent walls
one wall, one coat more
Landlord turns
the whole-unit bill
Methodology & Editorial Standards
Computation runs in IEEE-754 double precision at full internal precision; rounding to two decimal places occurs strictly at the display layer, so no cumulative drift enters the result. All monetary outputs use accounting presentation — grouped thousands, two decimals, negatives in parentheses — so figures can be transcribed directly into a model or working paper. Division-by-zero and out-of-domain inputs return an em-dash rather than a misleading number.
This engine was reconciled against an independent reference implementation and hand-verified for the worked example above before release. Our full five-stage review process is published on the About Us page.
Disclaimer. This calculator is provided for informational and modelling purposes only and does not constitute financial, tax, legal, medical, or engineering advice. Verify all figures with a qualified professional before acting on them.
Paint Color Coverage Calculator — 8 Expert FAQs
8 analyst-written answers to the questions practitioners actually ask — optimised for voice and answer-engine retrieval.
How much area does a gallon of paint really cover?
The can says 350-400 sq ft; real walls with texture, cut-in waste, and an amateur roller land nearer 300-350. The 350 default splits the difference on purpose. Rough or bare surfaces drink more; smooth primed walls drink less. If the can's number and the page's default disagree, trust the can — the manufacturer measured that product, and the page measures only arithmetic.
Do I need two coats, or is one enough?
Two for color, honestly — the second coat is what evens the sheen and kills the streaks the first one hides. One coat survives on same-color refreshes over sound paint. Dark over light, or any bare drywall, wants a primer first and primer is its own coat in the arithmetic: add it to the coat count rather than hoping. The default is 2 because the one-coat promise on the label is marketing with a straight face.
How do I account for doors and windows?
A standard door is about 20 sq ft and a typical window 15; deduct them in the openings field and the arithmetic forgives you honestly. Do not deduct trim you plan to paint — trim is its own small job with its own can. The field refuses deductions at or above the wall area, because at that point the room is a doorway and the honest answer is a quart, not a calculator.
Why round up to the whole gallon?
Three reasons with paint on them: cut-in brushwork wastes, rollers hold more than they return, and the leftover quart is what makes next year's scuff a five-minute fix instead of a color-matching archaeology project. Stores sell quarts, but a quart of a tinted match is never quite the can you bought. The page rounds the purchase up and says so; the decimal is the truth, the ceiling is the plan.
How do I measure wall area in the first place?
Perimeter times height, minus the openings: walk the tape around the room, multiply by ceiling height, and subtract doors and windows. A 12-by-15 bedroom with 8-foot ceilings carries about 432 sq ft of wall before deductions. Ceilings and trim are separate surfaces with separate arithmetic — add them as their own entries rather than inflating one number that then lies about two jobs.
Does paint quality change coverage?
Yes, and the coverage field is where you say so. Better paints carry more solids, hide in one coat more often, and justify 400 sq ft a gallon; budget paints at 300, or less on bare or dark surfaces. Deep, saturated colors are the worst hiders regardless of price — they want a tinted primer under them, which is the coat count again. The arithmetic stays the same; only the can's honest number moves.
How much does an accent wall cost?
About a quarter of the room, because one wall of four is 25% of the perimeter — the arithmetic scales linearly and the page prices whatever area you enter. One accent wall in the default room runs about 108 sq ft, one coat each of primer and color ≈ 0.62 gallons, so buy a gallon and keep the rest for the bookcase you will eventually paint to match. Enter the wall, not the room, and the page does the rest.
Is the second coat really necessary on dark colors?
More than ever — dark pigments are the weakest hiders in the store, and reds and deep blues routinely want two coats plus a tinted gray primer under them, which is three passes through this arithmetic. Enter coats=3 and watch the bill double against intuition; that is the page working. The alternative — one thick coat — sags, runs, and dries uneven, which is why painters say two thin coats and mean it as physics, not slogan.