HomeCostGuidePaint Calculator
Estimate paint quantity and cost from room dimensions.
Updated August 2026
Your project
Estimate
$53–$105
- Wall area
- 302 sq ft
- Paint needed
- 1.73 gal
- Recommended purchase
- 1.75 gal
Methodology
Wall area is calculated from room perimeter × wall height, minus a standard deduction for doors and windows, then divided by average paint coverage (350 sq ft per gallon) and multiplied by your number of coats.
How this calculator works
The calculator finds your wall perimeter from room length and width, multiplies it by wall height to get gross wall area, then subtracts a standard deduction per door (20 sq ft) and window (15 sq ft) — openings you don't have to paint. That net area is divided by 350 sq ft of coverage per gallon (a typical mid-grade interior paint) and multiplied by your number of coats, then rounded up to the nearest quarter-gallon since paint is sold in fixed can sizes.
Inputs explained
- Room length & width
- Floor dimensions in feet, used to calculate the room's wall perimeter (2 × (length + width)).
- Wall height
- Ceiling height in feet. Multiplied by the perimeter to get total gross wall area before deductions.
- Doors & windows
- Each door deducts 20 sq ft and each window deducts 15 sq ft from the paintable wall area — standard trade estimating deductions.
- Number of coats
- Most rooms need two coats for even color, especially over a different existing color. One coat may suffice for touch-ups or same-color repaints.
Example calculation
A 12×10 room with 8-ft ceilings, one door, and two windows has a 44-ft perimeter and 352 sq ft of gross wall area. Subtracting 50 sq ft for the door and windows leaves 302 sq ft of paintable wall. At two coats and 350 sq ft of coverage per gallon, that's about 1.75 gallons — roughly $53–$105 in paint at $30–$60 per gallon.
What affects your total cost
Paint itself is a small share of a full room repaint — labor (prep, taping, cutting in, cleanup) usually costs more than the material. Premium and specialty finishes (semi-gloss trim paint, ceiling paint, primer for drastic color changes or bare drywall) add cost beyond the flat per-gallon range used here. See our bathroom and kitchen remodel guides for how paint fits into a larger project budget.
Regional cost differences
Paint material pricing is fairly consistent nationwide, but labor rates for hired painting vary with local cost of living. Check your state's page under Locations for a regional labor cost adjustment if you're pricing out a professional paint job rather than DIYing it.
Frequently asked questions
Does this calculator include labor cost?+
No — it estimates material cost only (paint by the gallon). If you're hiring a painter, labor is typically priced separately, often per square foot or per room, and varies significantly by region and prep work required.
What if my room isn't a simple rectangle?+
Break an irregular room into rectangular sections, run each through the calculator separately, and add the results together. For rooms with vaulted or sloped ceilings, use an average height as a reasonable approximation.
Should I buy the exact amount calculated?+
We round up to the nearest quarter-gallon and recommend buying slightly more than the exact requirement to account for touch-ups later and avoid a mid-project run to the store — paint batches can vary slightly between purchases.
These estimates follow our published cost estimation methodology. They’re a planning starting point, not a contractor quote — actual costs vary by location, material choice, and project complexity.