Quick answer: A 12×12 room with standard 8-foot ceilings has about 351 square feet of paintable wall space (after one door and one window). For 2 coats, you'll need 2.2 gallons. Buy 2.5 gallons — two 1-gallon cans plus one quart — to cover touch-up work.
A 12×12 room is the most common size for a standard bedroom, home office, or guest room in North America. It's big enough that most people underestimate how much paint they need — and a second trip to the store risks a batch mismatch on touch-ups.
Use the interactive calculator below to dial in your exact dimensions, then check the breakdown table for a finish-by-finish comparison.
Figures below assume 8-foot ceilings, one standard door (3×7 ft), and one window (3×4 ft). Paintable wall area: 351 sq ft. Standard coverage rate: 350 sq ft per gallon.
Coats
Paint finish
Paintable area
Base estimate
Buy this much
1 coat
Any finish
351 sq ft
1.0 gal
1 gallon
2 coats recommended
Eggshell / Satin
702 sq ft total
2.0 gal
2.5 gallons
2 coats
Semi-gloss
702 sq ft total
2.2 gal
2.5 gallons
2 coats
Matte / flat
702 sq ft total
1.8 gal
2 gallons
3 coats
Any finish (dark colours)
1,053 sq ft total
3.0 gal
3.5 gallons
Including the ceiling?
A 12×12 ceiling is 144 sq ft. You'll need approximately 0.9 quarts — just buy one quart of flat white ceiling paint. This is separate from your wall paint; ceiling-specific formula reduces roller lines and dries without sheen.
What you're painting
Area
Paint needed (2 coats)
Recommended purchase
Walls only
351 sq ft
2.2 gal
2.5 gallons
Ceiling only
144 sq ft
0.8 gal
1 quart
Walls + ceiling
495 sq ft
3.0 gal total
2.5 gal walls + 1 qt ceiling
Which paint finish is right for your room?
The finish you choose affects both appearance and durability. Here's a quick guide for a 12×12 bedroom, office, or guest room:
Eggshell
Low sheen, easy to clean, hides minor imperfections
Best for bedrooms
Satin
Medium sheen, more washable — great for kids' rooms
Great choice
Semi-gloss
High sheen, very durable — better suited for trim and doors
Better for trim
Matte / Flat
No sheen, hides texture well — but marks easily
Ceilings only
Tips to get better coverage in a 12×12 room
🧱
Assess your wall surface
Smooth, prepped drywall gets the most coverage per gallon. Textured walls and bare drywall absorb significantly more paint — budget an extra 15–20%.
🎨
Use a tinted primer
If you're changing colours dramatically, ask the paint store to tint your primer close to your finish colour. This often eliminates the need for a third coat.
📦
Buy from one batch
Paint cans from the same batch are mixed to the same formula. Different batches can have subtle colour shifts. Always check the lot number on the bottom of the cans.
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Keep a touch-up can
Store leftover paint in a smaller, airtight jar labelled with the room and colour code. Even a half-cup is enough for scuff repairs years later.
Frequently asked questions
A 12×12 room with 8-foot ceilings has about 351 sq ft of paintable walls. For 2 coats you need roughly 2.2 gallons; buy 2.5 gallons (two 1-gallon cans + one quart) to include a 10% touch-up buffer.
Not for two coats. One gallon covers about 350 sq ft, enough for a single light coat. For the recommended two coats on a 12×12 room, plan for at least 2 gallons.
Eggshell is the most popular choice for bedrooms. It has a soft, low sheen, holds up to occasional cleaning, and looks great in both natural and artificial light. Satin is a slightly more durable option if the room gets heavy use.
Allow a full day. Budget 1–2 hours for prep (taping, covering furniture, patching holes), 1 hour per coat, and 2–4 hours of drying time between coats. A professional can do it in 3–4 hours total.
Primer is required if you're painting bare or patched drywall, going from a very dark to a very light colour, or painting over a glossy surface. For a simple colour refresh on a previously painted wall in good condition, you can skip primer with quality paint.
9-foot ceilings add about 48 sq ft of wall space (an extra foot of wall on each of the four sides). You'd need roughly 2.5 gallons for 2 coats instead of 2.2. Use the calculator above — just change the ceiling height field.
Get your exact paint estimate
Adjust for your real ceiling height, number of doors, and windows. The calculator generates a complete supply list with links to buy everything at once.