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Paint Calculator

Calculate gallons of paint needed for any room or wall, with door and window deductions.

Paint needed
2.1 gallons
9 quarts

Walls (ft)

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Paint needed
2.1 gallons
9 quarts · 365 sqft · 2 coats
Estimated cost
$105.00
Round up to 3 gallons
Total wall area
416 sqft
Net (after doors/windows): 365 sqft

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How to use the Paint Calculator

  1. 1

    Enter your inputs

    Fill in the required fields at the top of the paint calculator. Each input shows a default placeholder so you can see the expected format and units before you type.

  2. 2

    Adjust assumptions and options

    Use the toggles, sliders and dropdowns to tailor the calculation to your situation — currency, country, time period, advanced options and any optional fields all change the result in real time.

  3. 3

    Review the result

    The result card updates instantly as you type. Read the headline number, then check the breakdown, chart and any per-period schedule to understand how the inputs combined to produce the answer.

  4. 4

    Compare scenarios

    Change one input at a time to see how sensitive the result is to that variable. This is how you build intuition: small changes that move the answer a lot are the levers that matter.

  5. 5

    Share or save your result

    Copy the shareable link to send the exact scenario to someone else, or use your browser to print or save the page. The URL preserves every input so the recipient sees the same answer you do.

Frequently Asked Questions

  • Calculate wall area in square feet, subtract doors/windows, divide by coverage rate (typical 350 sq ft/gallon), multiply by number of coats.

  • Most paints cover 300-400 sq ft per gallon. Textured walls or porous surfaces cover less. Smooth, primed walls cover at the upper end.

  • Yes for: bare drywall, dramatic color changes, stains, glossy surfaces. Skip primer when repainting similar colors over previously painted, well-prepared walls.

  • Two coats is standard. One coat may suffice with high-quality paint over similar colors. Three coats for dramatic color changes (e.g., white over deep red).

  • Yes — standard door is ~21 sq ft, standard window ~15 sq ft. Subtract before calculating gallons. Don't deduct for outlets/switches (negligible).

  • Flat: matte, hides flaws, hard to clean. Eggshell: slight sheen, washable. Satin: smooth, durable. Semi-gloss: very durable, used for trim/bath/kitchen.

  • Roughly 1 gallon per 350 linear feet of trim, double for two coats. For windows and doors, estimate per piece (1 quart per 4-5 windows).

  • Ceilings typically need only one coat with dedicated ceiling paint. Calculate area separately at the same coverage rate.

  • Exterior often requires more paint per square foot due to texture and porosity. Use 250-300 sq ft/gallon estimate for siding.

  • Buy 5-10% extra for touch-ups and color matching. Custom-mixed colors are difficult to match exactly later.

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