How Much Paint Do You Need?
Enter your room size — get gallons to buy with a can breakdown, and primer only when your walls actually need it.
Last updated: July 5, 2026
Room Size (ft)
Openings (not painted)
Include ceiling (same paint)
Paint Order Summary
2
gallons of paint (2 coats)
Paint — 1-gallon can× 2
PrimerNot needed
Paintable Area339 sq ft
Per Coat1 gal
eggshell finish · 2 coats · doors/windows deducted · walls only · 10% waste
Worked Examples
12×12 Bedroom — 2 Coats
- Walls 384 sq ft − 1 door − 2 windows ≈ 339 sq ft
- Eggshell, 2 coats → 2 gallons (2 × 1-gal cans) · no primer
16×20 Living Room — 2 Coats
- Walls 576 sq ft − 2 doors − 3 windows ≈ 498 sq ft
- 2 coats → 3 gallons (3 × 1-gal cans)
New Drywall — 12×14 Office
- Bare surface → primer added to the list (covers ~300 sq ft/gal)
- Prime first, then two finish coats cover evenly
Paint Coverage by Finish
| Finish | Coverage / gal | Best For |
|---|---|---|
| Flat / Matte | ~400 sq ft | Ceilings, low-traffic rooms |
| Eggshell | ~375 sq ft | Living rooms, bedrooms — most popular |
| Satin | ~375 sq ft | Kitchens, bathrooms, hallways |
| Semi-Gloss | ~350 sq ft | Bathrooms, kitchens, trim |
| High-Gloss | ~350 sq ft | Doors, cabinets, trim |
Coverage rates per Paint Quality Institute guidance; rough or bare surfaces cover less.
When Do You Need Primer?
| Surface | Primer? | Why |
|---|---|---|
| Previously painted, good shape | No | Paint bonds fine to sound paint |
| Patched / repaired spots | Spot-prime | Patches flash through finish coats |
| Bare drywall or wood | Yes | Seals the surface, evens absorption |
| Dark color → light color | Yes (tinted) | Cuts the coats needed to hide it |
Frequently Asked Questions
A 12×12 room with 8-foot ceilings has about 384 sq ft of wall. Subtract a door and two windows and you're near 340 sq ft — two coats of eggshell needs about 2 gallons. Skip the ceiling and trim in that count; they're separate jobs. Enter your own room above for an exact can count.
Plan on 350-400 sq ft per gallon per coat on smooth, previously painted walls. Flat paint stretches a bit further (~400), glossier finishes cover a bit less. Rough, patched, or bare surfaces soak up more, which is why the calculator adjusts coverage by finish and surface condition.
Yes on bare drywall, bare wood, patched walls, or when covering a dark color — primer seals the surface so your paint covers evenly in fewer coats. Previously painted walls in good shape usually don't need it. Set the surface condition above and the calculator adds primer to your shopping list only when it's actually needed (primer covers ~300 sq ft/gal).
Two coats is the standard for a uniform color and sheen. One coat only works with premium one-coat paint over a similar color. Going dramatically lighter over dark walls can take two coats plus a tinted primer. The default here is 2.
A 5-gallon bucket costs less per gallon and means fewer can swaps, so it wins once you need 5+ gallons — typical for two coats in a large room or multiple rooms. Under 5 gallons, buy 1-gallon cans so you're not storing leftovers. The shopping list above breaks your total into the cheapest combination.
Walls only by default. Tick 'Include ceiling' to add the ceiling area using the same paint — fine for quick jobs, though ceilings usually use flat ceiling paint (see the Ceiling Paint Calculator). Trim, doors, and baseboards use semi-gloss and are best estimated separately.
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