Paint Calculator
Find how much paint you need and what it will cost for your project.
Your Details
Breakdown
Visual split of the key components
- Paint Cost92
Sensitivity
How the result changes across a range
How It Works
- Enter the values on the left.
- Press Calculate to see your results and charts.
- Use Reset to start over from the defaults.
Formula Used
Coverage per gallon is typically 300-400 sqft; check your specific paint's label.
Good to Know
- • Darker color changes often need an extra coat.
- • Primer may be needed separately on new drywall or big color changes.
Important Notes
- • Rounds up to the nearest partial gallon to avoid running short.
- • Doesn't include primer, tape, or supplies.
Why Coverage Estimates Vary
A paint can's stated coverage — often 300 to 400 square feet per gallon — assumes a smooth, properly prepped surface and even, standard-thickness application. Textured walls, porous or unprimed surfaces, and especially a significant color change (light-over-dark being the most demanding case) can noticeably reduce actual coverage compared to the label figure, sometimes requiring 20-30% more paint than a naive calculation would suggest.
It's generally safer to round up rather than risk running short mid-project — a partially finished wall left overnight while you buy more paint can dry with a visible line, and matching a paint color exactly on a second purchase (especially from a different batch or if the product has been reformulated) isn't always guaranteed, even with the same brand and product name.
Don't Forget Primer and Trim
This calculator estimates wall paint only. New drywall, significant color changes, or stain-prone areas (like water damage or smoke stains) often benefit from — or absolutely require — a separate primer coat before the finish coats go on, which is a distinct cost and material need not captured in a simple wall-paint calculation.
Trim, ceilings, and doors typically use different paint types (often higher-sheen or specialty formulations) priced and calculated separately from the main wall coverage, and their surface area needs its own measurement and gallon estimate rather than being lumped into the wall total.
A Few Terms Worth Defining
- Coverage rate — how many square feet one gallon of paint typically covers in a single coat.
- Coats — the number of paint layers applied; two coats is standard for most color changes and provides more even, durable coverage.
- Primer — a preparatory coat applied before paint, improving adhesion and blocking stains or drastic color changes.
See It In Action: Painting a Bedroom
400 square feet of wall area, 2 coats, 350 sqft/gallon coverage, $40/gallon:
Gallons needed = 800 ÷ 350 ≈ 2.29, rounded up to 2.5-3 gallons
Cost at $40/gallon ≈ $100-120
If the room needed a third coat for full coverage of a dramatic color change (say, painting over a dark accent wall with a pale color), the gallon requirement would rise to roughly 3.4, pushing the realistic purchase to 3.5-4 gallons and the cost to $140-160.
Room Size Comparison Table
| Room Size | Gallons Needed (2 coats) |
|---|---|
| Small bedroom (300 sqft) | ~2 gal |
| Living room (600 sqft) | ~3.5 gal |
| Whole floor (2,000 sqft) | ~11.5 gal |
Frequent Errors Estimating Paint Needs
- Not rounding up — running short mid-project means color matching a second purchase, which isn't always seamless.
- Ignoring surface texture — textured or porous walls absorb noticeably more paint than smooth, previously painted ones.
- Skipping primer on a major color change — without it, dark colors can bleed through lighter topcoats, requiring extra finish coats to fully cover.