PROJECT SUMMARY
Paint project summary
Wall paint2 gal · 2 coats
- Room
- 12 × 10 ft · 8 ft walls
- Paintable area
- 301 sq ft
- Primer
- None
- Ceiling
- Walls only
- Trim / doors
- Not painting
- Difficulty
- Beginner
- Build time
- 1 day
- Estimated materials
- $110–$148
Paint Calculator
Gallons, primer and cost for any room, by size, coats and paint quality.
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Paint calculator
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Estimates are planning aids, not a professional quote. Double-check quantities and product coverage — and any local code or permit requirements — before you buy.
⚠ Homes built before 1978 can have lead-based paint. Test suspect layers before sanding or scraping, and follow lead-safe practices — dust from old paint is a serious hazard, especially to children.
⚠ Ventilate the room and choose a low-VOC paint where you can. Open windows, run a fan, and take breaks — fumes build up fast in a closed room.
⚠ Work off a stable ladder or step stool on a level floor, never the top rung, and never overreach — move the ladder instead.
Cost breakdown
Material only · national-average rates
| Finishing & Sealant | $95–$129 |
| Fasteners & Hardware | $14–$20 |
| Total | $110–$148 |
Excludes tools, delivery, tax and permit fees. Labor not included — this is a DIY materials estimate.
Shopping list
Every item · grouped by store sectionThese are affiliate links: we may earn a commission if you buy through them, at no extra cost to you. It never changes what the calculator recommends — the shopping list comes from your dimensions, not from what pays.
Fasteners & Hardware
- 2× eaRoller covers — 3/8 in nap for most walls · one per coat
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- 1× eaAngled sash brush — cutting in edges & corners
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Finishing & Sealant
- 2× galInterior paint — Standard — 301 sq ft wall · 2 coats · 350 sq ft/gal
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- 2× rollsPainter's tape — 1.5 in · masking edges & trim
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- 1× eaCanvas drop cloths — protect floors & furniture
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Tools
✓ required · ○ helpful
- Roller frame & extension pole — pole saves your back and ladder trips
- Paint tray & liners
- Angled sash brush (2–2.5 in) — cutting in
- Painter's tape
- Drop cloths
- 5-in-1 painter's tool — scraping, spreading filler, cleaning rollers
- Spackle / filler & putty knife — patching nail holes and dings
- Sanding sponge / pole sander
- Step ladder
- Painter's rags & bucket
Project notes
- Paint is estimated by area: the wall perimeter times the height, minus the openings, times the number of coats, divided by the paint's spread rate (350 sq ft per gallon is typical for a smooth, previously painted wall).
- New drywall, big color changes and stained patches drink paint and need primer first — a tinted primer can even save a finish coat. Fresh, rough or dark surfaces cover less than the label's spread rate, so round up.
- Two coats is the honest standard for an even, durable finish; one coat only works going over the same color with premium paint. Buy all your wall paint at once and box (combine) the cans so the color is perfectly consistent.
- Cut in the edges with a brush, then roll the field in a 'W' pattern and lay it off in one direction while it's wet to avoid lap marks. Keep a wet edge and don't overwork the paint as it starts to set.
About this calculator
How to estimate a paint
Enter a room's length, width and wall height, tell the Paint Calculator how many doors and windows to subtract and how many coats you're rolling, and it returns the gallons of paint and primer to buy — plus tape, drop cloths, roller covers and a cost estimate. It nets out the openings so you don't overbuy, and switches to quarts when a small job needs less than a gallon.
Pick a paint quality, add the ceiling or trim if you're painting those too, and the takeoff updates instantly. Buy all the wall paint at once and box the cans together so the color stays dead consistent from the first wall to the last.
Step by step
How to paint a room
A step-by-step walkthrough to go with your plan above. Follow the product instructions and any local code or permit requirements as you work.
- 1
Clear and prep the room
Move furniture out or to the center and cover it, take down switch and outlet covers, and spread drop cloths. Wash greasy or dusty walls and let them dry — paint won't bond to grime.
- 2
Tape and mask
Run painter's tape along trim, ceiling lines, windows and door casings, pressing the edge down firmly with a 5-in-1 tool so paint can't creep underneath. Mask off anything you're not painting.
- 3
Patch and sand
Fill nail holes, dings and cracks with spackle, let it dry, then sand smooth along with any glossy or rough spots. Wipe off the dust with a damp cloth so the surface is clean and flat.
- 4
Prime where needed
Spot-prime patches and stains, or roll a full coat of primer on new drywall, bare wood or a big color change. Let it dry fully before the color goes on.
- 5
Cut in the edges
With an angled sash brush, paint a 2–3 inch band along the ceiling, corners, trim and around openings — the places a roller can't reach cleanly. Work one wall at a time so the cut-in stays wet.
- 6
Roll the walls
Load the roller evenly and roll the field in a large 'W' or 'M', then fill it in without lifting, working in sections while the cut-in is still wet to blend the edges and avoid lap marks.
- 7
Second coat
Let the first coat dry for the time on the can (usually 2–4 hours), then repeat the cut-in and roll. The second coat is what gives you full, even coverage and true color.
- 8
Pull tape and clean up
Remove the tape at a 45-degree angle while the last coat is still slightly wet for the crispest line, then reinstall the covers and let everything cure. Wash brushes and rollers or bag them for the next coat.
Equip the job
Recommended gear for this build
Hand-picked categories that match the shopping list above. Links open a current selection so you can compare brands and prices.
These are affiliate links: we may earn a commission if you buy through them, at no extra cost to you. It never changes what the calculator recommends — the shopping list comes from your dimensions, not from what pays.
Finishing & SealantInterior latex wall paintA washable eggshell or satin covers well and cleans up with water — buy all your gallons at once and box them.
$28–65/gal
Finishing & SealantPainter's masking tapeClean lines along trim and ceilings; pull it while the last coat is still slightly wet.
$6–9/roll
Finishing & SealantCanvas drop clothsReusable and non-slip, unlike plastic — the one thing that saves your floors.
$10–25 ea
Finishing & SealantPrimer / stain-blockerSeals new drywall, patches and stains so the finish coat covers evenly.
$25–40/gal
Tools5-in-1 tool + roller trayThe everyday painter's multitool plus a tray with liners for quick color changes.
$15–30
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Answers
Frequently asked questions
How many gallons of paint for a 12×12 room?
A 12×12 room with 8-foot walls has about 384 square feet of wall, or roughly 340 after subtracting a door and a couple of windows. At two coats and 350 square feet per gallon, that's about 2 gallons of wall paint. This calculator does the math for your exact size, coats and openings, and drops to quarts when a small job needs less than a gallon.
How much does it cost to paint a room?
For a typical bedroom, DIY materials — paint, primer, tape, roller covers and drop cloths — usually run about $80–200 depending on paint quality and whether you prime. Premium paint costs more per gallon but often covers in fewer coats and lasts longer. The calculator totals your specific materials so you can see the range before you shop; it doesn't include labor.
Do I need to prime before painting?
Prime when you're painting new drywall, bare wood, or fresh patches, when you're making a big color change (especially light over dark), or when you're covering stains, smoke or glossy surfaces. Over an existing similar color in sound condition, a quality self-priming paint is usually enough. Turn on 'Prime first' and the calculator adds primer sized to the wall area.
How many coats of paint do I need?
Two coats is the standard for an even, durable finish and true color. One coat only holds up when you're going over the same color with a premium paint, and drastic color changes or deep colors can need three. More coats means more paint, so set the count and the estimate scales with it.