Measure the Room
Enter the room length, width and wall height. The calculator uses those measurements to estimate the complete wall surface around the room.
Gross wall area =
2 × (length + width) × height
Gallop Home Tool
Paint Calculator
Estimate paint and primer for room walls and ceilings, including recommended can sizes and project cost.
Metric Calculator
PAINT PLANNING GUIDE
Plan Paint Quantity, Coats and Project Cost Before You Buy
A reliable paint estimate starts with the surface area, then adjusts for doors, windows, coats, product coverage and any ceiling or primer work. Use these six planning steps with the calculator above to prepare a more realistic material estimate.
Subtract Doors and Windows
Doors and windows normally do not require wall paint. Enter their combined areas so they are removed from the gross wall area.
Net wall area =
gross wall area − openings
Choose the Number of Coats
One coat uses less material, while two or more coats increase the coated area. New surfaces, major colour changes and some finishes may need additional coats.
Coated wall area =
net wall area × coats
Use the Paint Coverage Rate
Check the manufacturer's stated coverage in square metres per litre. Different paint types and surface conditions can produce different real-world coverage.
Paint litres =
coated area ÷ coverage rate
Add Ceiling and Primer When Needed
Ceiling paint and primer are optional in this tool. When enabled, their areas, coats and coverage rates are calculated separately from the main wall paint.
Ceiling area =
length × width
Review Cans and Material Cost
The calculator recommends a combination of 20 L, 10 L, 4 L and 1 L cans that provides enough paint while reducing unnecessary leftover material. Enter paint and primer prices to estimate material cost.
Estimated total =
paint cost + primer cost
Use the Result as a Planning Estimate
Actual paint use can change with surface porosity, texture, preparation, application method, colour change and the specific product being used. Check the coverage information on the paint you intend to buy before making the final purchase.
The calculator estimates material quantities and basic paint and primer cost. Labour, preparation, repairs, tools, masking materials, delivery and other project expenses are not included.