Paint Calculator
How much interior paint you need by room size and number of coats.
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Interior painting is the highest-impact, most beginner-friendly home project there is. The finish quality is 90% prep and patience — the actual rolling is the easy part.
DifficultyBeginner
TimeA weekend per room, including prep and two coats
SkillsNo special skills — just a steady hand for cutting in edges
Tools you'll need
- Roller frame, covers (3/8" nap for walls), and a tray
- Angled sash brush for cutting in
- Painter's tape and drop cloths
- Spackle, putty knife, and sandpaper
- Primer (for patches, stains, or big color changes)
- Extension pole and a sturdy ladder
Step by step
- Clear and clean the walls Move furniture out, then wash walls (especially kitchens) so paint bonds. Dust and grease are why paint peels.
- Patch, sand, and tape Fill nail holes and dents, sand smooth, then tape trim and cover floors. Good lines start with well-pressed tape.
- Prime where needed Spot-prime patches, stains, and bare drywall — and prime the whole wall for a drastic color change or when going light over dark.
- Cut in the edges Brush a 2–3" band along the ceiling, corners, and trim before you roll, so the roller can get close without hitting them.
- Roll in sections Load the roller and roll a 3×3 ft "W", then fill it in. Keep a wet edge and don't over-spread — a fuller coat hides better than a thin, stretched one.
- Second coat and pull the tape Let the first coat dry per the can, apply the second, then peel the tape while the paint is still slightly wet to avoid lifting dried paint.
Common mistakes
Skipping cleaning and prep
Wash, patch, and sand first. Paint only looks as good as the surface under it.
No primer over patches or color changes
Patches and dark colors flash through. Spot-prime repairs and prime fully for big color jumps.
Overloading the roller
Drips and roller marks come from too much paint at once. Load lightly and work in small sections.
Not boxing the paint
If you have multiple cans, mix ("box") them together first so the color is identical wall to wall.
Peeling tape after the paint dries
Dried paint bridges the tape edge and tears. Pull tape while the last coat is still slightly wet, or score the edge first.
Safety
- Open windows and ventilate, even with low-VOC paint.
- Set ladders on level ground and don't overreach — move the ladder instead.
Frequently asked questions
How many coats of paint do I need?
Two coats is standard for an even, durable finish. One coat may cover a same-color refresh; big color changes can need a primer plus two coats.
Do I need primer?
Prime bare drywall, patched spots, stains, and any large or light-over-dark color change. Repaints in a similar color usually don't need it.
How much paint do I need?
Enter your room size, wall height, and number of coats above — the calculator returns gallons to buy at 350 sq ft per gallon.
How much does a gallon of paint cover?
About 350 square feet per coat on smooth walls — less on textured or porous surfaces.