Paint Calculator
Use this paint calculator to estimate how many gallons of paint you need for a room, accent wall, ceiling, or multi-wall project. It accounts for wall area, doors, windows, number of coats, paint coverage, waste factor, and optional price per gallon so you can plan a realistic shopping list.
Subtracts 21 sq ft each
Subtracts 15 sq ft each
Typical: 2 coats for most projects
Square feet per gallon (check paint can)
Leave empty to skip cost calculation
Typical: 10% for most projects
Paintable Area
96.00
square feet (doors/windows subtracted)
Gallons Required (Exact)
0.60
2 coats with 10% waste
Quarts Equivalent
2.41
if buying in quarts
Suggested Gallons to Buy
1
rounded up to nearest gallon
Formula:
Gallons = (Paintable Area × Coats × (1 + Waste)) ÷ Coverage
Assumptions:
- Doors subtract 21 sq ft each
- Windows subtract 15 sq ft each
- Coverage varies by paint type and surface texture
- Waste accounts for spillage and touch-ups
Planning estimate only
These calculations provide planning estimates. Always verify with product specifications and professional guidance before purchasing materials.
What this paint calculator does
Use this paint calculator to estimate how many gallons of paint you need for a room, accent wall, ceiling, or multi-wall project. It accounts for wall area, doors, windows, number of coats, paint coverage, waste factor, and optional price per gallon so you can plan a realistic shopping list.
Material Tally calculators are built for planning conversations with suppliers, contractors, and family members before a project starts. They help you see the difference between exact math and practical buying quantities, including waste factors and rounded purchase units. The result should be treated as a strong planning estimate, then checked against product labels, supplier guidance, and local building requirements.
Best for
- Early material planning before visiting a supplier
- Comparing cost assumptions and waste factors
- Checking whether a project is small enough for bagged or boxed materials
- Creating a clearer shopping list before work begins
How to use the calculator
Enter each wall height and width, or switch to direct square footage mode if you already measured the paintable area.
Add the number of standard doors and windows so their approximate area can be subtracted.
Set the number of coats. Two coats are common for color changes or new drywall primer plus finish work.
Use the coverage rate from the paint label when available, because different products cover different areas.
Review exact gallons, rounded gallons to buy, quart equivalents, and optional cost.
How the math works
The calculator multiplies wall height by wall width for each wall, then subtracts estimated door and window areas. It multiplies the paintable area by the number of coats, divides by the coverage rate per gallon, and then adds the selected waste factor. The final buying recommendation rounds up to whole gallons because most interior paint is purchased by the gallon.
Planning tips
Coverage rates on paint cans assume a smooth, sealed surface. Textured walls, fresh drywall, masonry, and dramatic color changes can reduce real coverage.
If you are painting trim, doors, cabinets, or ceilings in a different product, estimate those separately instead of folding everything into one wall calculation.
Keep a small amount of leftover paint for future touch-ups. Buying exactly the calculated amount can make repairs difficult if the color batch is no longer available.
For best results, confirm primer needs and coating instructions on the product label, especially for bathrooms, kitchens, exterior surfaces, or stain-blocking work.
Frequently asked questions
Related tools and guides
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Related guides
- How to Calculate Paint for a Room
Estimate wall paint by measuring wall area, subtracting openings, choosing coats, and applying real coverage rates.
- Paint Coverage, Coats, and Waste Factor Explained
Understand why paint coverage varies and how coats, primer, texture, color changes, and waste factor affect gallons.
- Estimating Waste by Material Type
Choose better waste factors by separating breakage, cuts, spillage, compaction, and product packaging across material types.
- Material Estimate Checklist Before You Buy
Use this checklist to review measurements, waste, product specs, delivery, code issues, and supplier questions before purchasing materials.