Paint Calculator - Gallons Needed for Walls, Ceilings & Rooms
Enter the room length, width, and wall height instead of trying to figure out wall square footage yourself. You can subtract windows/doors and add ceiling or other extra area in advanced settings.
Last updated: August 2026
Buying and sizing notes
- For dark color changes, porous surfaces, textured walls, or bare drywall, plan extra paint or primer.
- Keep a labeled leftover container for touch-ups.
How to use this estimate
What this includes
- Room length and width
- wall height
- coats
- coverage per gallon
- openings and extra areas when entered
What it does not include
- wall repairs
- primer selection
- trim and doors unless included in extra area
- paint product-specific coverage guarantees
Common mistakes
- Using floor square footage as wall square footage
- forgetting the second coat
- ignoring texture or repairs
- assuming every paint covers the same
Quick questions
How do I estimate paint gallons for a room?
Use the room perimeter times wall height, multiply by coats, subtract major openings if desired, then divide by the paint coverage per gallon.
Should I include ceilings and trim?
Only include ceilings, trim, doors, and closets if you plan to paint them. They can change both paint quantity and labor.
Common paint examples
Paint gallons depend on wall area, ceiling area, coats, color change, texture, and paint coverage.
One room
Use room length, width, and wall height. Add coats, then check whether ceilings, trim, closets, and doors are included.
Dark-to-light color change
Color changes can need primer or extra coats, which changes gallons and labor more than room size suggests.
Textured or repaired walls
Texture and repairs can increase paint use and prep time. A cheap quote may exclude the prep that makes the finish look right.
Painting project reality check
This estimates paint gallons. A real painting quote is often driven by prep, repairs, masking, trim, ceilings, coats, and access.
- wall repairs
- primer
- color changes
- ceilings
- trim
- doors
- furniture moving
- floor protection
- paint product line
Next steps for this project
Use these related paths when the calculator result turns into a real buying decision, budget, or quote comparison.
Related guide
Use the guide with this calculator when you need more context before buying materials or comparing options.
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