Paint Calculator: How Much Paint Do I Need?
Enter your room dimensions and the calculator estimates how many gallons of paint and primer you need, with a cost range across budget, standard, and premium product tiers. It accounts for doors, windows, ceiling height, and the number of coats so the estimate matches what you actually need to buy.
Room details
Defaults work for a typical bedroom. Adjust to match your room.
You need
Finish paint
0gallons
Primer
0gallons
Estimated total cost
$0–$0
Surface area
0sq ft
How we calculated this
Paint quality tiers and what to expect
Buying one to two gallons more than the calculator suggests is normal and gives you touch-up paint that matches the rest.
Budget interior paints run $20 to $30 per gallon and almost always need two or three coats. Standard mid-tier paints run $35 to $55 per gallon, cover most walls in two coats, and hold up reasonably well in low-traffic rooms. Premium paints run $55 to $90 per gallon, often cover in one or two coats, and last noticeably longer in bathrooms, kitchens, and high-traffic areas. For DIY projects where your labor is free, mid-tier usually wins; for any wall you do not want to repaint for a decade, premium pays for itself.
Frequently asked questions
How accurate is this?
Estimates are typically within 10 to 15 percent of actual usage for standard rectangular rooms with average wall texture. Heavily textured walls (orange peel, knockdown, popcorn) absorb more paint than smooth drywall. Dark-to-light color changes can push usage higher. Round up at the store.
Should I buy extra?
Yes. Buy about 10 percent more than the calculator suggests, then keep the leftover for touch-ups in a sealed can stored upside-down. Paint formulations shift slightly between batches, so matching the same color months later is hard. The leftover from your original batch is the only reliable touch-up source.
Do I need primer?
Yes for new drywall, bare wood, glossy surfaces (including previously painted trim), dark-to-light color changes, and anywhere with stains. No if repainting in the same color over an existing finish in good condition. Some premium paints include primer-like adhesion and can skip a separate primer coat on already-painted surfaces.
How many coats?
Two coats is the default for most projects. Premium paints can sometimes cover in one coat over similar colors. Going from dark to light, covering stains, or painting over significant patchwork typically needs three coats plus primer. Always plan for two coats unless you have specific reason to expect one will do.
What about ceilings?
Check the include-ceiling box and the calculator adds the floor square footage as ceiling area. Ceiling paint is usually a separate flat or ultra-flat product (tinted blue or pink to show where you have rolled) and the spread rate is similar to wall paint. For bathrooms, use a satin mildew-resistant ceiling paint instead of flat.