Paint Calculator
Calculate exactly how much paint you need for any room. Get accurate gallon counts, cost estimates, and a complete shopping list.
Calculate Your Paint Needs
Find out how much paint to buy for your room
Room Dimensions (feet)
~21 sq ft each
~12 sq ft each
Best coverage: ~400 sq ft/gallon
Total Paint Needed
3 gallons
387 sq ft with 2 coats
387 sq ft
$206
What You Need
387 sq ft walls
$120
89 linear ft trim
$36
Tape, rollers, brushes, trays
$50
Time Estimate
Don't Forget
- Painter's tape
- Drop cloths
- Rollers & covers
- Paint tray
- Brushes (2-3")
- Extension pole
- Stir sticks
- Rags/paper towels
- -Primer improves coverage and adhesion, especially over dark colors
- -Always buy slightly more paint than calculated for touch-ups
- -Stir paint thoroughly and maintain a wet edge to avoid lap marks
How to Use This Calculator
Enter your room dimensions in feet - length, width, and wall height. Standard ceiling height is 8 feet; many newer homes have 9 or 10-foot ceilings.
Enter the number of doors and windows to subtract from the paintable area. The calculator uses average sizes (21 sq ft for doors, 15 sq ft for windows).
Select number of coats - two is standard for most projects. Choose your paint quality based on your budget and the room's use.
Check the options for primer (recommended for most projects) and trim paint if you're painting baseboards and door frames too.
Understanding Your Results
The gallons needed includes a 10% waste factor for drips, roller absorption, and touch-ups. Always round up - you can return unopened gallons.
The shopping list shows everything you need with estimated prices. Prices vary by brand and location - these are average home improvement store prices.
Time estimate includes prep work (taping, covering furniture), painting, and cleanup. Actual time varies based on experience and wall condition.
The "Don't Forget" list shows supplies you'll need beyond paint. Having everything ready before you start makes the job much smoother.
Frequently Asked Questions
How much paint do I need for a 12x12 room?
A 12x12 room with 8-foot ceilings has about 384 square feet of wall space. After subtracting doors and windows, you typically need 1.5-2 gallons for two coats. One gallon covers approximately 350-400 square feet per coat.
How many coats of paint do I need?
Two coats is standard for most painting projects. Use one coat only for touch-ups or when using a paint-and-primer combo over a similar color. Use three coats when making dramatic color changes (especially light over dark), painting over repairs, or for high-traffic areas.
Do I need primer before painting?
Primer is recommended for: new drywall, stained or patched areas, color changes (especially dark to light), glossy surfaces, and wood surfaces. Many modern paints include primer, but a separate primer provides better coverage and adhesion for challenging surfaces.
What's the difference between paint qualities?
Economy paint is thinner, requires more coats, and fades faster. Standard paint offers good coverage and durability for most rooms. Premium paint has better coverage (often one-coat), superior durability, easier cleaning, and better fade resistance - worth it for high-traffic areas and exteriors.
How long does it take to paint a room?
A 12x12 room typically takes 4-6 hours for a DIY painter, including prep, two coats, and cleanup. Factors affecting time: ceiling height, number of doors/windows, wall condition, color changes, and experience level. Add 2-4 hours for primer if needed.
Should I buy extra paint?
Yes, buy 10-15% more than calculated for touch-ups, mistakes, and future repairs. Keep leftover paint for touch-ups - store it properly (sealed, room temperature) and it can last 10+ years. Most stores accept returns of unopened gallons.
Related Calculators
Found this calculator helpful?
Check out our other free calculators for everyday math problems.
View All Calculators