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Paint Quantity Calculator — How Many Gallons Do I Need?
Can I DIY? · DIY-FriendlyEnter your wall area, coats, and openings to get exact gallons of paint and primer, plus a materials-only DIY cost estimate.
Educational calculators — always consult a licensed professional before making financial decisions.
Estimate: (room perimeter in feet) × (wall height in feet). A 12×12 room with 8 ft ceilings is roughly 320 sq ft of wall.
Two coats is standard for most color changes.
Standard recommendation for most jobs.
We'll subtract their area from your total wall square footage.
Ceiling paint and primer are commonly needed alongside wall paint.
Walls only, no primer.
This changes the price per gallon used in your material cost estimate.
$35–$55/gallon typical.
Paint needed
2 gallons
Estimated material cost: $100 – $190
Material Cost Breakdown
Where Your Money Goes
Based on 350 sq ft of coverage per gallon, a standard industry assumption. Actual coverage varies by paint brand, surface texture, and application method. Materials only — no labor cost is included.
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What you'll need
- ·Wall area in square feet (perimeter × ceiling height)
- ·Number of coats you plan to apply
- ·How many doors and windows are in the space
What you'll get
- ✓Gallons of paint needed — Rounded up to the nearest quart-gallon
- ✓Primer quantity — If you're covering a major color change or new drywall
- ✓Materials-only cost range — Paint, primer, and sundries — no labor
Paint coverage overview
Planning to hire a painter instead? Try our Painting Cost Calculator for a full labor + materials estimate, or see our DIY painting guide for step-by-step instructions.
How it works
Enter your wall area
Perimeter × ceiling height, in square feet.
Set coats and openings
Number of coats plus how many doors and windows to deduct.
Add ceiling, primer, and quality tier
Get exact gallons needed and a materials-only cost range.
Paint Coverage Reference
| Item | Typical Rate |
|---|---|
| Coverage per gallon | 350–400 sq ft per coat |
| Door deduction | ~20 sq ft each |
| Window deduction | ~15 sq ft each |
| Economy paint | $25 – $35 / gallon |
| Standard paint | $35 – $55 / gallon |
| Premium paint | $55 – $80 / gallon |
Textured surfaces, unprimed drywall, or dramatic color changes reduce real-world coverage — buy slightly extra.
About this calculator
How much paint do I need for a room?+
A standard 12×12 room with 8 ft ceilings has roughly 320 sq ft of wall area. At 350 sq ft of coverage per gallon and 2 coats, that's about 2 gallons of wall paint after subtracting doors and windows. Use this calculator with your actual wall square footage for a precise number.
How many square feet does a gallon of paint cover?+
A gallon of paint typically covers 350–400 sq ft per coat on a smooth wall. Textured surfaces, unprimed drywall, or darker color changes can reduce coverage to 250–300 sq ft per gallon — buy slightly extra rather than running short mid-coat.
Do I need primer before painting?+
Primer is worth using for a major color change (especially dark to light), painting over glossy paint, or covering new or patched drywall. For a same-color refresh on an already-painted wall in good condition, primer usually isn't necessary.
Want to try different numbers?
Back to the calculator ↑Paint Quantity Calculator is built and maintained by the RealCostIQ editorial team. Cost ranges and rates are checked against published industry data and contractor quotes, and revised when the underlying figures move. Read our data methodology or more about who builds this. Every calculation runs in your browser — no account, and none of your inputs are stored.
Cost ranges and rates here are checked against contractor quotes and published industry data. If a number still looks off, email Support@RealCostIQ.com and we'll review and fix it.