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How Much Paint for a 10×12 Room with a 9 ft Ceiling?

A 10 × 12 room with a 9 foot ceiling needs this much paint per coat, with doors and windows already deducted. Here is the answer, plus a calculator you can adjust if your measurements are slightly different.

Answer: 2 gallons

How it changes with coats

Same area, different coats:

Coats	1	2	3
Paint needed	1 gallon	2 gallons	3 gallons
Openings deducted	51 ft²	51 ft²	51 ft²

What a 10×12 room with a 9 ft ceiling actually involves

At 10×12 ft this is the size of a typical bedroom, home office or dining room. Stripping out the openings leaves about 345 ft² of wall to cover, and at 2 coats that is 690 ft² of paint. It is a comfortable one-person weekend job, and the only real decision is whether to roll or spray.

Four walls give 396 ft² of raw surface. After 1 door and 2 windows — deducted at 21 ft² and 15 ft² each — you are painting 345 ft². At 2 coats and 350 ft² per gallon, that rounds up to 2 gallons. Everything below comes from those figures.

Where the square footage goes

Surface	Area	Notes
Two 12 ft walls	216 ft²	12 ft × 9 ft each
Two 10 ft walls	180 ft²	10 ft × 9 ft each
Walls, gross	396 ft²	perimeter of 44 ft × 9 ft ceiling
Doors deducted	21 ft²	1 × 21 ft²
Windows deducted	30 ft²	2 × 15 ft²
Paintable wall	345 ft²	what the 2 gallons actually covers

The footprint is 10 ft × 12 ft, so the two 12 ft walls are the long runs and the two 10 ft walls are the short ends. The long walls roll quickly; the short ends carry the corners and usually the door, so allow more cutting-in time per foot there.

At 9 ft the top of the wall sits at the awkward height where a stepladder is a stretch but scaffolding is overkill; an extension pole and a stable platform are the practical answer.

Working at a 9 ft ceiling

At 9 ft the ceiling line is out of reach from the floor but too low to justify scaffolding. The practical setup is a 6 ft platform stepladder plus an extension pole on the roller. Budget about 6 repositioning moves around the 44 ft perimeter — more than an 8 ft room, and it is the top few inches where a rushed cut-in shows.

One coat, two coats, three coats

Most repaints need two coats, but the quantity changes sharply with each pass, so it is worth seeing the three side by side:

Coats	Paint required	Typical use
1	1 gallon	same colour, already primed, or a touch-up
2	2 gallons	the standard: full colour change and durability
3	3 gallons	dark over light, bare drywall, or a deep accent colour

This page is worked through at 2 coats, which is why the answer box says 2 gallons. If you are painting a dark wall back to a light colour, treat two coats as the minimum and buy for three — running out mid-wall is worse than a spare can.

Ceiling, trim and primer — the extras

The calculator covers walls only. If you are doing the whole room, these are the add-ons:

Item	Quantity	Notes
Ceiling	120 ft² — about 1 gallon per coat	10 ft × 12 ft flat area, priced as a separate surface
Baseboard and trim	41 lin ft — about 1 quart	trim paint covers roughly 100 linear ft per quart
Primer	1 gallon	one coat over 345 ft²; needed over bare drywall or a dark colour

Primer is usually cheaper per gallon than colour and does two jobs: it seals bare drywall so the topcoat does not get sucked in, and it lets a colour change cover properly in two coats instead of three. Skimping on primer is the most common reason a two-coat job turns into a four-coat job.

Buying the paint

Option	Quantity	Estimated cost
Single gallons	2	$76
5 gallon pail	not worth it below 5 gal	—

At 2 gallons you are below the level where a 5 gallon pail pays off, so buy single cans. Buy them all in one trip and check the batch codes match: two cans from different batches can be slightly different tints, and a wall repainted from a mismatched can shows the seam forever.

Costs assume $38 per gallon and $165 per 5 gallon pail of mid-range interior paint ($30 per gallon of primer, $16 per quart of trim enamel). Brand, sheen and finish move these numbers a lot, so treat them as a planning figure rather than a quote.

Common questions

How much paint for a 10×12 room?

2 gallons of wall paint. That covers 690 ft² of surface at 2 coats, after deducting 1 door and 2 windows from the 396 ft² of wall. A 1-coat refresh would take 1 gallon and a 3-coat job 3.

Does that include the ceiling and trim?

No. The 2 gallons is for the four walls. The ceiling adds 120 ft², about 1 gallon per coat, and the baseboard and trim come to roughly 41 linear ft, about 1 quart of enamel. Add them to the order if you are doing the whole room.

How much primer do I need for this room?

About 1 gallon for one coat over the 345 ft² of paintable wall. Primer is only needed over bare drywall, fresh patching or a big colour change — over a similar existing colour you can skip it and go straight to two coats of paint.

How long between coats for a room this size?

Water-based interior paint is usually recoatable in two to four hours at normal room temperature. In a room this size, plan to finish a full pass before starting the next — that naturally spaces the coats and keeps the finish even. Cold, humid weather stretches the wait; check the can rather than guessing.