Paint calculator
Estimate paint gallons for room walls and ceilings.
What this calculator covers
Estimate how much paint a rectangular room needs for its walls and optional ceiling.
The walkthrough keeps the coverage math visible so users can see how openings, coat count, and coverage rate change the gallons required.
Frequently asked questions
- How many square feet does a gallon of paint cover?
- Coverage varies by paint type and surface texture. Typical interior latex paint covers roughly 350 square feet per gallon on smooth surfaces, while rough or porous surfaces can drop that to around 250 square feet. The calculator lets you select the coverage rate that matches your surface.
- Should I buy extra paint beyond the calculated amount?
- The result already rounds up to the next whole gallon for purchase planning. Whether you need an additional buffer depends on how many touch-ups you anticipate and whether the color will be discontinued. A common rule of thumb is to keep one extra quart for touch-ups on large projects.
- Why are doors and windows subtracted from the total area?
- Doors and windows are not painted surfaces in most jobs, so subtracting their combined area from the gross wall area gives a more accurate paintable surface before multiplying by the number of coats.
- Does the coat count affect how many gallons I need?
- Yes. Two coats requires roughly twice the paint of one coat because the same surface area is covered twice. The total coated area used in the calculation is paintable area multiplied by the selected coat count.
Tool
Run the calculation
Result
RESULT · PAINT
â„–016
Primary result
3 gallons
A 12 ft by 10 ft room with 8 ft walls needs about 3 gallons of paint to buy for 2 coats.
- Paintable area
- 451 sq ft
- Total coated area
- 902 sq ft
- Gallons to buy
- 3 gallons
Step-by-step solution
- 1.Find the wall area from perimeter × wall height, then add the ceiling if selected to get a gross paint area that displays as 472 sq ft.
- 2.Subtract 21 sq ft of openings to get 451 sq ft of paintable surface.
- 3.Multiply by 2 coats and divide the exact coated area by 350 sq ft per gallon. The fractional paint need displays as 2.58 gallons, and the purchase recommendation rounds up to 3 gallons.
Walkthrough
Visual walkthrough
Paint planning starts with the surfaces in the room, removes openings, multiplies by the coat count, and then converts that coated area into gallons.
01
Measure walls and optional ceiling
2 × (12 + 10) × 8 = 352 sq ft
Perimeter times wall height gives wall coverage, and the ceiling can be added when it is part of the paint job, with the displayed areas rounded for readability.
02
Remove openings and apply coat count
Doors and windows are subtracted before the remaining paintable area is multiplied by the number of coats.
902 sq ft of coated area
03
Convert coverage into gallons
Coverage rates vary by paint and surface, so the exact coated area is divided by the selected coverage rate and then rounded up for purchase planning.
3 gallons to buy