Paint Calculator
Figure out how many gallons of paint to buy for any room — walls, ceiling, doors and windows subtracted, multiple coats, primer, U.S. pricing, and a downloadable PDF material list.
Coverage varies by paint, color change, and surface — always check the can (usually 350-400 sq ft/gal). Dark-to-light changes may need an extra coat. For planning purposes only.
| Coats | Paint Area | Gallons | Paint Cost | Cost / sq ft |
|---|
For your 333 sq ft of paintable surface. More coats = more gallons and better color depth.
How to use the paint calculator
Four quick steps turn your room size into a full paint order — gallons for the walls and ceiling, doors and windows subtracted, primer and supplies — with U.S. pricing, a coats comparison, and a downloadable PDF.
Enter the room
Length, width, and ceiling height; choose whether to paint the ceiling and subtract doors and windows.
Set coats & surface
Pick 1, 2, or 3 coats and your surface type — the coverage per gallon updates to match.
Choose grade & extras
Pick a paint grade, set the waste %, and add primer, supplies, or a labor rate if you want.
Read results & save a PDF
Get gallons, a full cost breakdown, a coats comparison, and a downloadable material list.
How the paint estimate is calculated
It starts from your wall area, adds the ceiling if you’re painting it, and subtracts the doors and windows you’ll skip. Then it multiplies by coats, divides by coverage, and rounds up to whole gallons. Here is the exact math behind each output.
Worked example — a 12 ft × 12 ft bedroom, 8 ft ceilings, 1 door + 2 windows, 2 coats
Wall area: 2 × (12 + 12) × 8 = 384 sq ft
Openings: (1 × 21) + (2 × 15) = 51 sq ft
Net area: 384 − 51 = 333 sq ft → Paint area (2 coats): 333 × 2 = 666 sq ft
Gallons (+10%): (666 ÷ 400) × 1.10 = 1.83 → 2 gal | Paint cost: 2 × $42 = $84
≈ 2 gallons for 2 coats over 333 sq ft, about $84 in standard paint at $42 / gallon.
Paint estimating charts
Handy lookups for the questions people ask most — gallons by room size, how surface and coats change coverage, and typical U.S. costs. Figures use the calculator’s defaults (2 coats, +10% waste), so always confirm your own can’s coverage.
| Room | Wall area | Net (–1 door/2 win) | Gallons (2 coats) |
|---|---|---|---|
| 8 × 10 | 288 sq ft | 237 sq ft | 2 gal |
| 12 × 12 | 384 sq ft | 333 sq ft | 2 gal |
| 12 × 14 | 416 sq ft | 365 sq ft | 3 gal |
| 15 × 20 | 560 sq ft | 509 sq ft | 3 gal |
| 20 × 25 | 720 sq ft | 669 sq ft | 4 gal |
Wall area = 2 × (length + width) × height, less ~21 sq ft per door and ~15 sq ft per window. Add length × width if you’re painting the ceiling too. Coverage assumes 400 sq ft/gallon.
| Surface | Coverage / gallon | Notes |
|---|---|---|
| Smooth, previously painted | ~400 sq ft | The easy case; best coverage |
| Light texture (orange peel) | ~350 sq ft | Slightly more paint into the texture |
| Heavy texture / stucco / brick | ~275 sq ft | Deep profile drinks paint |
| New / bare drywall | ~350 sq ft + primer | Prime first, then topcoat |
Rougher and more porous surfaces cover less, so they need more paint for the same area. Bare drywall should be primed before the finish coats go on.
| Net paintable area | 1 coat | 2 coats | 3 coats |
|---|---|---|---|
| 150 sq ft | 1 gal | 1 gal | 2 gal |
| 250 sq ft | 1 gal | 2 gal | 3 gal |
| 350 sq ft | 1 gal | 2 gal | 3 gal |
| 500 sq ft | 2 gal | 3 gal | 5 gal |
| 750 sq ft | 3 gal | 5 gal | 7 gal |
| 1,000 sq ft | 3 gal | 6 gal | 9 gal |
Gallons = (net area × coats ÷ coverage) × 1.10, rounded up to whole cans. Each extra coat multiplies the paint you need, so a color change costs more than a refresh.
| Grade | Typical U.S. price | Best for |
|---|---|---|
| Economy / builder | $20–$35 / gallon | Rentals, closets, quick jobs; often needs a coat more |
| Standard | $35–$50 / gallon | Most rooms; solid coverage in 2 coats |
| Premium (paint + primer) | $50–$80 / gallon | Best hide & durability; sometimes one-coat capable |
| Primer | ~$30 / gallon | Bare drywall, patches, stains, big color changes |
| Supplies | ~$40–$80 / room | Rollers, tray, brushes, tape, drop cloths |
2024–2025 U.S. ballparks matching the calculator’s defaults. Premium paint costs more per gallon but hides better and can save a coat, so cost per finished room is often closer than it looks. Your local prices will vary.
2×(L+W)×H
optional add-on
subtracted
Paint covers the surfaces, not the floor. The calculator builds the paintable area from your walls, optionally adds the ceiling, and takes the openings back out.
- Walls — perimeter times ceiling height: 2 × (L + W) × H, the bulk of the job.
- Ceiling — add length × width only when you’re painting it; it often takes its own color.
- Doors & windows — subtracted at ~21 and ~15 sq ft each so you don’t buy paint for glass.
Everything the calculator works out
One set of room dimensions gives you a complete paint order — the gallons, the primer, the supplies, and a costed coats comparison.
Key figures every paint job depends on
Built for any painting project
From a single accent wall to a whole-house repaint, the same calculator scales to the room, the surface, and the number of coats.
Repainting a bedroom or living room and wants to buy the right number of gallons without a second trip.
- Start from a preset like Bedroom 12×12
- Plan on 2 coats for an even finish
- Keep a quart for touch-ups
Quoting rooms and needs paint, primer, supplies, and labor per square foot in one place to bid fast.
- Set surface type for real coverage
- Add a labor rate for a full bid
- Save the PDF material list for the quote
Repainting units on a budget and comparing economy versus standard paint on total cost per room.
- Compare grades on cost per gallon
- Prime patches and stains to save a coat
- Total gallons across every room
7 tips for an accurate paint order
Small habits keep your count right and your finish even, consistent, and easy to touch up later.
Paint calculator FAQ
The gallons, coverage, coats, and U.S. cost questions people ask most before buying paint.
Work out the wall area as 2 × (length + width) × ceiling height, add the ceiling if you’re painting it, then subtract about 21 sq ft per door and 15 sq ft per window. Multiply that net area by the number of coats and divide by the paint’s coverage.
A 12 × 12 ft room with 8 ft ceilings, one door and two windows has about 333 sq ft of paintable wall. At two coats and 400 sq ft per gallon, that’s about 2 gallons.
Most interior wall paint covers about 350 to 400 sq ft per gallon in one coat on a smooth, previously painted surface. Textured, porous, or bare surfaces cover less.
Rough guides: smooth walls about 400 sq ft, light orange-peel texture about 350, and heavy texture, stucco, or brick closer to 275 sq ft per gallon. Always check the can for your specific product.
Two coats is the standard for a durable, even finish and is what most manufacturers recommend. One coat may be enough for a same-color refresh with premium paint.
Plan on three coats for a big color change, going light over dark, or with deep and bold colors that hide poorly. Each extra coat multiplies the paint you need.
Yes, for a tighter estimate you subtract the openings you won’t paint. A standard interior door is about 21 sq ft and an average window about 15 sq ft.
For a 12 × 12 room with one door and two windows, that’s roughly 51 sq ft removed from the wall area. Skipping this step just means you buy a little extra, which is often fine as built-in waste.
Prime bare drywall, patched areas, stains, and big color changes so the topcoat colors stay even and you may save a coat of paint. Bare drywall in particular soaks up paint and should always be primed first.
Over clean, previously painted walls in a similar color you can usually skip separate primer, especially with a paint-and-primer product. Primer is applied as a single coat and covers a bit less than paint.
In the U.S., economy or builder-grade paint runs about $20 to $35 per gallon, standard paint about $35 to $50, and premium paint-and-primer roughly $50 to $80.
Premium paint costs more per gallon but hides better and can save a coat, so the cost per finished room is often closer than the sticker price suggests. Add primer, supplies, and labor if you hire out.
Allow about 10% extra to cover cutting in, roller loss, and touch-ups, and bump it higher for rooms with lots of corners or if you’re spraying, which wastes more.
Buy all your paint from the same batch, or box the cans together, so the color stays consistent across the room. Keep about a quart sealed for touch-ups after the furniture moves back in.
Going light over dark usually needs a tinted primer plus two coats, or two to three coats of a quality paint-and-primer, because light colors have less hiding power.
A gray-tinted primer helps the new color reach its true shade faster and can save a topcoat. Set the calculator to three coats for these jobs so you don’t come up short.
General Estimating Notice: This calculator sizes paint, primer, supplies, and cost from your room dimensions, surface, coats, coverage, and the prices you enter, using typical 2024–2025 U.S. figures. Actual coverage varies by paint, color change, surface texture, application method, and applicator, so always check the can’s coverage and prime bare or patched surfaces. Dark-to-light color changes may need an extra coat. Buy from one batch for consistent color and keep some paint for touch-ups. For planning purposes only.