PAINT CALCULATOR
Find out exactly how many gallons of paint you need. Enter your room dimensions, subtract doors and windows, pick your coverage rate, and get an instant cost estimate.
Pre-filled with a 14 x 12 ft living room. Adjust dimensions or add more rooms below.
Wall Area
416 sq ft
PAINT SETTINGS
YOUR ESTIMATE
3
gallons needed
$135
estimated paint cost @ $45/gal
BREAKDOWN
Rounded up from 2.1 to 3 gallons. Always buy whole gallons.
How Much Paint Do I Need?
The standard rule: one gallon covers about 350 sq ft of smooth wall with a single coat. Most interior jobs need two coats, so plan for roughly 175 sq ft of actual wall per gallon. Textured surfaces like stucco or brick and stone drop that to 250-300 sq ft per gallon.
Standard Coverage
350 sq ft / gal
Typical Coats
2 coats
Avg. Gallon Cost
$30 - $70
How to Calculate Paint by Room Size
- Measure wall area. Multiply the room perimeter (length + width, doubled) by the ceiling height. A 12 x 12 ft room with 8 ft ceilings = 384 sq ft of wall.
- Subtract openings. A standard door is about 21 sq ft, a window about 15 sq ft. Two doors + two windows = 72 sq ft less to paint.
- Factor in coats. Multiply paintable area by the number of coats. Going from a dark to a light color? Budget three coats. Same shade refresh? One coat may do.
- Divide by coverage rate. Divide total sq ft by your paint’s coverage rate (check the can label). Round up to the next whole gallon. See our paint sheen guide for how finish type affects coverage.
Coverage Rates by Paint Type
| Paint Type | Coverage (sq ft/gal) | Best For |
|---|---|---|
| Latex / Acrylic | 350 - 400 | Most interior walls |
| Oil-Based / Alkyd | 350 - 450 | Trim, cabinets, high-moisture |
| Primer | 200 - 300 | New drywall, stain blocking |
| Textured / Elastomeric | 150 - 250 | Stucco, masonry, concrete |
Coverage varies by brand. Premium paints like Benjamin Moore and Sherwin-Williams typically deliver higher coverage per gallon than budget options.
Pro Tips for Accurate Estimates
Don't forget trim and ceilings
This calculator covers wall paint. Trim, baseboards, and ceilings use different amounts. See our guide on painting trim and baseboards for separate estimates.
Application method matters
Sprayers use 20-25% more paint than rollers. If you’re using a sprayer, bump your estimate by a quarter gallon per gallon. Learn more in our sprayer guide.
Buy an extra gallon for touch-ups
Keep leftover paint for future nicks and scuffs. Paint colors can shift between production batches — buying all at once ensures a perfect match.
Ready to turn your estimate into a client proposal? Use our painting estimate template or interior painting cost calculator to price the full job including labor. For step-by-step instructions, see how to paint a room.
RELATED TOOLS & GUIDES
Interior Painting Cost Calculator
Estimate the full cost of an interior paint job including labor, materials, and prep.
How Much Does It Cost to Paint a Room?
Detailed cost breakdown by room size, paint quality, and whether you hire a pro.
How to Paint a Room
Step-by-step guide from prep to final coat for a professional finish.
How Much Does It Cost to Paint a House?
Interior and exterior painting costs with pricing per square foot.
Deck Stain Calculator
Estimate how much stain or sealant you need for your deck project.