Painting tool
Paint Calculator
Get gallons and cost in under a minute. Enter room dimensions, subtract doors and windows, and get a clean, practical estimate.
What this tool solves
- • Calculates exact paint gallons needed.
- • Subtracts doors and windows automatically.
- • Includes primer and ceiling options.
- • Estimates total material cost.
Enter room dimensions
Measure wall-to-wall interior dimensions.
Estimates only. Coverage varies by paint quality and surface.
Step 1: Room size
Step 2: Doors & windows
Step 3: Paint options
Paint estimate
Based on 2 coats at 350 sq ft per gallon (Eggshell / Satin), plus a 10% buffer.
3 gallons of paint
Calculated: 2.7 gallons (rounded up)
Selected finish: Eggshell / Satin
Estimated cost
Does not include brushes, rollers, tape, or drop cloths.
Visualize paint colors first?
Upload a room photo and see different wall colors with AI before you buy.
Try AI Room StylerPaint calculator FAQs
How much paint do I need for a 12x12 room?
A 12x12 room with 9ft ceilings has about 432 sq ft of wall space. After subtracting a door and two windows, you need roughly 1.5-2 gallons for two coats. Use the calculator above for exact amounts.
How many square feet does a gallon of paint cover?
One gallon of paint typically covers 350-400 square feet per coat. Coverage varies by paint quality, surface texture, and application method. This calculator uses 350 sq ft as a conservative estimate.
Do I need primer before painting?
Primer is recommended when painting over dark colors, new drywall, patched areas, or stained surfaces. Many modern paints include primer, but separate primer provides better coverage and adhesion.
Should I buy extra paint?
Yes, buy 10-15% more than calculated for touch-ups, mistakes, and future repairs. This calculator rounds up to whole gallons which typically provides this buffer.
Explore more tools
Plan your full room project with spacing, budgets, and palettes.
Continue with ideas and playbooks
Once your paint quantities are set, explore room ideas and step-by-step playbooks to execute the full design.