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Paint Calculator for a 12×12 Room — How Many Gallons?

Free paint calculator pre-filled for a standard 12×12 bedroom or guest room. About 3 gallons of finish paint for 2 coats. Adjust inputs below for your specific room.

A 12×12 room is one of the most common bedroom sizes in American homes — and one of the most-searched paint quantity questions. Here's the answer up front: a standard 12×12 room with 8-foot ceilings, one door, and one window needs about 3 gallons of interior paint for 2 coats, plus a half gallon of primer if you're painting over a stain, going dark-to-light, or coating fresh drywall.

The calculator below is pre-filled for that exact scenario. Adjust the inputs if your room differs — vaulted ceilings, accent walls, multiple windows, etc. — and the math updates instantly. The materials shopping list further down links directly to Home Depot for the specific paint, primer, and supplies you'll need.

A few things people typically miss when calculating paint for a 12×12 bedroom:

  • Closet walls add 50-150 sq ft depending on closet size. If you're painting the closet too, add it as separate dimensions or treat it as a small follow-up project with its own quart of paint.
  • Trim and baseboards are not included in the wall paint calculation. Plan a separate quart of semi-gloss trim paint per room.
  • Ceilings are off by default. Toggle "Painting the ceiling?" if you want it included (~144 sq ft for a flat 12×12 ceiling, about half a gallon).
  • Sheen affects coverage by ~10%. Flat covers more per gallon than satin or semi-gloss. The calculator assumes the 350 sq ft/gallon midpoint that most paints publish.

If your room isn't a standard 12×12, the main paint calculator handles any dimensions.

How much paint for a 12×12 room?

Pre-filled for a 12×12 bedroom with 8-ft ceilings, 1 door, 1 window.

You need
  • Paint needed
    3 gallons
    348.00 sq ft × 2 coats, 350 sq ft/gal, 10% waste
  • Paintable area
    348.00 sq ft
    walls only, openings subtracted

What you'll need to buy

Prices approximate · Links go to retailer search results
Estimated total: ~$176 (materials, before tax)

Product links go to Home Depot search results — pick the best match for your project. Prices shown are rough averages.

How we calculated it

The math for a 12×12 room is the same formula used everywhere:

  1. Wall area = 2 × (12 + 12) × 8 = 384 sq ft
  2. Subtract openings — 21 sq ft (door) + 15 sq ft (window) = 36 sq ft
  3. Paintable area = 384 − 36 = 348 sq ft
  4. For 2 coats: 348 × 2 = 696 sq ft of paint coverage required
  5. Divide by 350 sq ft/gallon → 1.99 gallons
  6. Add 10% waste factor and round up → 3 gallons total (incl. touch-up buffer)

For a different room size — say 10×12, 14×16, or a non-rectangular space — adjust the length and width above and the math redoes itself instantly.

Assumptions: 10% waste, 350 sq ft/gal coverage on smooth interior drywall, 21 sq ft per door, 15 sq ft per window. These match Sherwin-Williams and Behr published figures.

Frequently asked questions

How many gallons of paint for a 12×12 bedroom with 8-foot ceilings?
About 3 gallons covers a 12×12 bedroom with 8-foot ceilings, one door, and one window for 2 coats — including the standard 10% waste factor. Skip a gallon if you are doing a single same-color refresh; add a gallon if you are including the ceiling or have multiple windows.
Do I need primer for a 12×12 bedroom?
Only if (1) the surface is fresh drywall, (2) you are going from dark to light, (3) you are covering stains or smoke damage, or (4) the existing paint is glossy. Otherwise, modern paint-and-primer-in-one finishes are fine for a same-tone repaint.
How much paint for a 12×12 room with vaulted ceilings?
Add roughly 30-50% more paint depending on peak height. A 12×12 room with a 12-foot peak adds about 150 sq ft of wall area — roughly one extra gallon for two coats. Set the wall height in the calculator to your average ceiling height (mid-point between low side and peak) for a quick estimate.
What's the cost to paint a 12×12 bedroom?
Materials run $60-150 (paint + primer + supplies). Painter pro labor adds $200-450 depending on region, prep work, and trim count. Most DIYers complete a 12×12 bedroom in a single weekend — half a day for prep + first coat, half a day for second coat after dry time.
What sheen for a 12×12 bedroom?
Eggshell or satin for walls — washable but not too shiny. Semi-gloss for trim, doors, and the closet interior. Flat only if the walls are very smooth and traffic is minimal (formal dining room, not a kid bedroom).
Should I include the ceiling in a 12×12 paint job?
If the ceiling has stains, age, or you are changing wall color significantly, yes — fresh ceiling paint makes the room feel newer. Add ~144 sq ft for a flat 12×12 ceiling, which is about half a gallon. Toggle 'Painting the ceiling?' in the calculator to include it.
How much trim paint for a 12×12 bedroom?
Plan a separate quart of trim paint per room. Standard 12×12 bedroom has ~50 linear feet of base trim plus one door frame plus one window frame — about 1 quart of semi-gloss covers all trim with 2 coats.

Painting a different room size?

The same calculator engine works for any size room. Use the main paint calculator with custom dimensions, or check our other common-size guides: