Paint Calculator
Enter your total wall area in square feet and the number of coats to find how many gallons of paint you need, plus a recommendation with 10% overage to avoid running short. Useful for any painting project from a single room to an entire house.
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Calculator
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Formula
Gallons = (Wall Area × Coats) ÷ 350
Standard latex paint covers approximately 350-400 square feet per gallon on a smooth surface. We use 350 as a conservative estimate to account for texture and absorption. Multiplying by the number of coats gives total coverage needed. The 10% buffer result adds waste for touch-ups, spills, and lap marks.
How to use the Paint Calculator
- 1
Enter your total wall area (sq ft)
- 2
Enter your number of coats
- 3
Read your results instantly
Results update in real time as you type.
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Calculating Wall Area
Measure the perimeter of the room in feet and multiply by the ceiling height to get the gross wall area. Subtract approximately 20 square feet per standard door (21 sq ft) and 15 square feet per window (15 sq ft) for a more accurate net area. For an accent wall or a single surface, just measure that wall's width times its height. Textured walls and rough surfaces absorb more paint — reduce the 350 coverage estimate to 300 sq ft/gallon for heavily textured surfaces.
One Coat vs. Two Coats
One coat of paint rarely provides full coverage, especially when changing colors. Two coats is the standard for a professional finish on most surfaces. Dark-to-light or light-to-dark color changes may need three coats. Using a primer before paint can reduce the number of topcoats needed and improve adhesion, especially on new drywall or drastically different colors. Factor primer into a separate calculation since its coverage rate may differ from your topcoat.
Tips & Insights
Buy in 5-Gallon Buckets
For projects needing 3+ gallons of the same color, a 5-gallon bucket is cheaper per gallon than individual quarts and ensures color consistency across the batch.
Round Up to the Next Gallon
Always buy a full gallon more than the exact estimate. Running out mid-wall and buying a second can of the same color can cause slight sheen differences.
Save Leftover Paint for Touch-Ups
Store leftover paint in a sealed can or airtight container. Label it with the room and color code so you can easily touch up scuffs years later.
Worked Examples
Average Living Room (400 sq ft, 2 coats)
2.29 gallons needed, 2.51 with 10% buffer — buy 3 gallons.
Large Open Floor Plan (800 sq ft, 2 coats)
4.57 gallons, 5.03 with buffer — buy a 5-gallon bucket.
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Frequently Asked Questions
How much does a gallon of paint cover?
Standard latex paint covers 350-400 square feet per gallon on a smooth surface. Rough or textured surfaces may only yield 250-300 sq ft per gallon.
Do I need to include the ceiling in my calculation?
Only if you are painting the ceiling. Measure ceiling area separately (length × width) and run a separate calculation, since ceiling paint often has different coverage rates.
Should I subtract door and window areas?
Yes, for a more accurate estimate. Subtract about 21 sq ft per door and 15 sq ft per standard window from your total wall area.
Why does texture affect paint coverage?
Textured surfaces have more total surface area than flat ones, and the peaks and valleys absorb more paint. Reduce the coverage estimate by 15-25% for heavily textured walls.
Is primer included in this calculation?
No. Primer is a separate product with its own coverage rate (typically 300-400 sq ft/gallon). Run this calculator separately for primer, using 1 coat and the primer's coverage rate.
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