Paint Coverage Calculator
Order paint from the three numbers that decide it: net area (surface minus doors and windows), the number of coats, and the coverage rate per gallon per coat. Coverage is the honest variable — smooth drywall takes roughly 350 ft²/gal while porous masonry can halve that — so the rate is an editable input with surface presets, not a hidden constant, and the answer is reported per coat and in total, with an optional primer coat. Free, no login.
Surface
Paint
Coverage is surface-dependent and editable; first/primer coats cover less. Round up to whole cans.
Paint — Material Order Sheet
Prepared with NORDIX — nordixhq.com/tools/paint-calculator
Net area: 1,140 ft² (1200 − 60 openings) · Surface: Smooth drywall · Coverage: 350 ft²/gal · Coats: 2
| Line item | Quantity | Notes |
|---|---|---|
| Finish paint | 6.51 gal | 2 coats × 3.26 gal per coat — round up to whole cans |
Coverage (ft²/gal per coat) is a manufacturer- and surface-dependent planning figure — smooth drywall ≈350, light texture ≈275, masonry/porous ≈150; first and primer coats cover less. Confirm the spread rate on the can and round up to purchasable can sizes.
How this calculator works
net area = area − openings · per coat = net ÷ coverage · total = per coat × coats (+ primer)
The arithmetic is exact; the coverage rate is a planning figure — manufacturer- and surface-dependent, which is why it stays editable. The presets (350 ft²/gal smooth drywall, 275 light texture, 150 masonry/porous) are typical mid-range values; the spread rate printed on the can or datasheet governs, and first coats over new or patched surfaces cover less than the rated figure. Round the result up to purchasable can sizes — the calculator reports exact gallons so you can decide between a fifth gallon and a quart.
Worked example
1,200 ft² of wall with 60 ft² of doors and windows, two coats at 350 ft²/gal:
- Net area: 1,200 − 60 = 1,140 ft².
- Per coat: 1,140 ÷ 350 = 3.26 gal.
- Two coats: 6.51 gal — buy 7 gallons, or a five plus two singles. Checking the primer box adds one more coat at the same rate (+3.26 gal).
Enter the same job above (1,200 ft², 60 deducted, 2 coats, 350) to reproduce it.
Reference: two-coat gallons by surface
Gallons for 1,000 ft² net at two coats, computed by the same engine at each surface preset. These are planning figures — porosity, texture, color change, and application method all move real coverage, so confirm against the spec or datasheet.
| Surface | Coverage (ft²/gal/coat) | 2 coats per 1,000 ft² |
|---|---|---|
| Smooth drywall | 350 | 5.71 gal |
| Light texture | 275 | 7.27 gal |
| Masonry / porous | 150 | 13.33 gal |
Frequently asked questions
How much area does a gallon of paint cover?
A typical figure is 350–400 ft² per gallon per coat on smooth, previously painted drywall — this calculator defaults to 350. Texture and porosity pull that down hard: light texture runs closer to 275 ft²/gal and bare masonry or other porous surfaces can drop to 150 ft²/gal or less, which is why the surface selector changes the coverage number. The rate printed on your paint's data sheet governs; the field is editable so you can enter it.
How much paint do I need for a 12×12 room?
Four walls at 8-ft ceilings is 4 × 12 × 8 = 384 ft² of wall. Deduct a door (~20 ft²) and a window or two (~15 ft² each) and you're near 330 ft² net — call it one gallon per coat at 350 ft²/gal, so two coats needs about 2 gallons of wall paint. Enter your real measurements above; the calculator nets out the openings and shows per-coat and total gallons.
How many coats of paint do I need?
Two finish coats is the standard spec for a uniform film and consistent sheen, and it's the calculator default. One coat can pass on a same-color repaint in good condition; drastic color changes — especially covering dark colors or painting deep reds and yellows — may need a tinted primer plus two coats. Primer is counted separately here, not as one of your finish coats.
Do I subtract windows and doors when measuring for paint?
Yes — unlike drywall, paint genuinely isn't applied over openings, so deducting them keeps the estimate honest. Standard rules of thumb: about 20 ft² per door and about 15 ft² per average window. Add those up and put the total in the doors/windows field; the calculator subtracts it from the gross wall area before figuring gallons.
Do I need primer, and how much?
Prime bare drywall, fresh joint compound, patched areas, stain-blocked spots, and any big color change; a sound previously painted surface in a similar color usually just needs the two finish coats. The primer checkbox adds one coat at the coverage rate you entered — note that first coats on new drywall tend to soak in and cover less than the nominal rate, so round up. Manufacturer data governs primer coverage too.
Should I round up to whole gallons?
Yes. Buy whole cans and round up — running out mid-wall risks a visible lap line, and leftover paint from the same batch is your touch-up stock. If the total lands just over a gallon multiple (say 2.1 gal), a quart may bridge the gap, but check the price: quarts often cost more than half a gallon, and gallon-count pricing breaks at 5-gal buckets on production work.
Method: net area ÷ coverage × coats, with openings deducted and an optional single primer coat at the same rate. Coverage per gallon per coat is an empirical planning figure — the presets are typical values for smooth drywall (≈350), light texture (≈275), and masonry/porous surfaces (≈150), but the manufacturer’s stated spread rate governs, and primer over bare substrates usually covers less than finish paint. The result is exact gallons, not cans: round up to purchasable sizes, and expect deep color changes or high-contrast repaints to need the full coat count the spec calls for.
Pair with the Square Footage Calculator to build the wall area, or the Drywall Sheet Calculator and Joint Compound Calculator for the surface that has to be hung and finished before the first coat goes on.