How many square feet does a gallon of paint cover?

About 350–400 square feet per coat on smooth, previously painted drywall, the rate printed on most interior paint labels. Textured walls take about 300 and masonry about 225 square feet per gallon.

How much primer do I need for new drywall?

Plan on about 300 square feet per gallon for one coat of drywall primer. Bare paper and joint compound absorb more than painted surfaces.

How many gallons of paint for a 12x12 room?

The walls of a 12 × 12 room with 8 ft ceilings are 384 square feet. Two coats at 400 square feet per gallon need 1.92 gallons, so buy 2 gallons. Ceiling and trim are extra.

Do I need two coats of paint?

Usually. Two coats give even colour and sheen and a thicker, more durable film. A single coat can work when repainting the same colour over sound paint.

Does a gallon of paint cover more with a sprayer?

No, usually less. Overspray and the thicker film from a sprayer typically use more paint than rolling the same area. Back-rolling after spraying improves adhesion on rough surfaces.

Paint Coverage Chart: Square Feet per Gallon by Surface

Typical square feet covered by one US gallon, one coat, for finish paint and primer
Surface	Paint ft²/gal	Primer ft²/gal	Typical range ft²/gal	Note
Smooth drywall, previously painted or sealed	400	300	350–400	The rate printed on most can labels.
Light texture / orange peel	300	250	275–325	Texture adds surface area.
Heavy texture / knockdown / popcorn	250	200	200–275	Roll with a 3/4 in nap or spray.
New, bare drywall	300	300	250–350	Paint rate is for porous, unprimed board (no maker publishes one; 300 is mid-range for porous surfaces). Drywall primers run 300–400; once primed, finish coats cover like smooth sealed drywall.
Bare wood (siding, trim)	300	300	250–350	Wood primers quote 350–400 on smooth stock; rough-sawn wood can drop to 150–200.
Masonry, stucco, brick	225	200	225–325	Rough stucco can drop to about 125 (paint) and 80 (primer); porous block may need block filler.
Metal (primed)	400	350	350–450	Use a metal primer on bare steel.

Typical primer and finish coats by situation
Situation	Primer coats	Finish coats	Note
Same or similar colour, sound existing paint	0	2	One coat can work for a refresh; two gives an even sheen.
Light colour over dark	1	2	Use a primer tinted toward the new colour.
Dark or saturated colour over light	1	2	Deep reds and yellows may need a third finish coat; a grey-tinted primer helps.
New drywall	1	2	PVA or drywall primer seals paper and mud evenly.
Bare wood or patched/stained areas	1	2	Stain-blocking primer over knots, water marks and smoke.

Paint for the walls of a room with 8 ft ceilings, 2 coats, no deduction for doors or windows
Room ft	Wall area ft²	Smooth at 400 gal	Buy (smooth) gal	Textured at 300 gal	Buy (textured) gal
10 × 10	320	1.60	2	2.13	3
12 × 12	384	1.92	2	2.56	3
12 × 15	432	2.16	3	2.88	3
15 × 20	560	2.80	3	3.73	4

How to read the coverage chart

Each row is a surface; the columns give typical square feet covered by one US gallon of finish paint and of primer for a single coat. To estimate paint, divide the area to be painted by the spread rate, then multiply by the number of coats. The "typical range" column shows how much the rate varies between products for that surface.

Worked example: a 12 × 14 ft bedroom with 8 ft walls has 2 × (12 + 14) × 8 = 416 ft² of wall. Subtract a door (about 20 ft²) and a window (about 15 ft²) for 381 ft². Two coats at 400 ft²/gal need 1.91 gallons, so 2 gallons will do the walls.

Why surfaces cover differently

A spread rate on the can assumes a smooth, sealed surface and a specific film thickness. Texture adds real surface area: an orange-peel or knockdown wall has more square inches than its flat dimensions suggest. Porous surfaces such as new drywall, bare wood and masonry soak up the first coat, which is why primers are rated lower and why priming first saves finish paint. Dark colours over light, and light over dark, often need a tinted primer and still two finish coats.

Planning coats

The coats table gives a starting point by situation. New drywall gets a primer and two finish coats. Repainting the same colour over sound paint can be one coat if the finish is uniform, but two is the safer plan. Water stains, smoke and knots need a stain-blocking primer, or they bleed through any number of finish coats.

Common paint coverage mistakes

Using the label rate for a textured or porous surface.
Forgetting the second coat when estimating.
Skipping primer on new drywall, which leaves joints visible through the paint (flashing).
Buying exactly the calculated amount; keep some for touch-ups from the same batch.

These are manufacturer-typical figures, not values for any one product. The technical data sheet for your paint lists its own spread rate and recoat time, and it takes precedence.

Reviewed October 11, 2026 by the Tradesman Calculator editorial team · Figures are from Manufacturer technical data sheets (Sherwin-Williams, Benjamin Moore, Zinsser, Kilz), typical ; local amendments may apply · Report an error

Paint coverage chart

Coverage per gallon by surface

How many coats

Gallons for common room sizes