Use our paint calculator to accurately estimate how much paint you need for any room or interior space. Enter your room dimensions, door and window openings, number of coats and paint coverage to calculate total paintable area and litres required. Ideal for planning interior painting, wall painting, ceiling painting and home renovation projects.
Paint Calculator
Estimate paint required (litres & cans) for one or more rooms — walls, ceilings, coats and wastage included.
Accurately estimating your paint requirements is essential before starting any interior painting project. This calculator helps you determine the exact litres needed based on your room dimensions, number of openings, coats of paint and the coverage rate of the product you plan to use. It is an essential tool for anyone planning interior wall painting, ceiling painting, or full room repainting.
For general pricing guidance, see our house painting cost guide.
The example shown uses a 4 m × 3 m × 2.6 m room with one door and one window. Two coats of paint were selected, with a coverage rate of 12 m² per litre and a 10% wastage allowance. The ceiling was included in the calculation. Based on these inputs, the calculator estimates a total paintable area of 45.16 m², requiring approximately 8.28 litres of paint. A suggested breakdown of can sizes is also provided for easier purchasing.
How the Calculator Works
- Measure each room
Enter the length, width and height of the room. The calculator automatically determines the wall area.
If you are unsure of measuring methods, visit our painting measurement guide. - Account for openings
Doors, windows and other openings reduce the total paintable area. Add their quantities or enter the total area of additional openings. - Choose the number of coats
Most interior surfaces require two coats for a consistent finish. Learn more in our interior painting guide. - Select the paint coverage rate
Paint products vary in coverage. Refer to the number listed on your paint can, or check our overview of paint types and coverage rates. - Adjust for wastage or overhead
A small allowance helps cover touch-ups, roller absorption, and minor spillages. Professionals typically allow 10–15%. - Include or exclude the ceiling
If you are repainting the ceiling, the calculator adds your room’s floor area. For ceiling-specific instructions, see our ceiling painting guide.
Understanding Your Results
Total Paintable Area
The combined area of all relevant surfaces (walls and ceiling if included), minus deductions for doors, windows and additional openings.
Estimated Litres Required
This figure reflects the total amount of paint needed once coats, coverage and wastage are applied.
Suggested Can Breakdown
The calculator suggests a practical mix of paint tin sizes, helping you purchase the closest amount without excessive leftover material.
For broader project cost expectations, see our interior painting prices.
Why Accurate Calculation Matters
Correctly estimating your paint requirements helps you:
- Avoid running out of paint mid-project
- Prevent unnecessary overspending
- Maintain consistent colour and finish across all surfaces
- Plan your time, materials and budget more effectively
Accurate calculations are especially important when working with premium paints or professional painting services where precision affects overall cost and scheduling.