How to Use the Paint Calculator

Choose whether you are painting a single wall or a whole room, then enter the required dimensions. Select Metric or Imperial units, add the number of coats you plan to apply, and enter the paint coverage rate shown on your paint container or product specifications.

If you want to deduct doors and windows, you can either enter their total area directly or choose "Help me calculate it" and enter the width, height, and quantity for doors and windows of the same size.

You can also enter the paint container size to estimate how many containers you may need. If you know the price per container, enter it to estimate the total paint cost.

How Paint Calculation Works

For a single wall, the calculator multiplies the wall width by the wall height to determine the wall area.

For a whole room, it calculates the perimeter using the room length and width, then multiplies the perimeter by the wall height.

Any door and window areas you enter are deducted from the wall area to calculate the paintable surface area. That area is then multiplied by the number of coats and divided by the paint coverage rate.

How Many Coats of Paint Do I Need?

The number of coats required depends on the paint, surface condition, colour change, primer, and manufacturer's instructions.

Two coats are often used for many interior painting projects, so the calculator starts with two coats by default. You can change this value to match your project.

Understanding Paint Coverage

Paint coverage tells you approximately how much surface area a given amount of paint can cover. Manufacturers usually provide a coverage rate on the paint container or product specifications.

Actual coverage can vary depending on the surface texture, porosity, application method, and paint product. Use the manufacturer's stated coverage whenever possible.

Should I Subtract Doors and Windows?

If there are doors, windows, or other openings that you do not plan to paint, you can subtract their area for a more tailored estimate.

If you already know the combined area of your doors and windows, choose I know the total area and enter it directly. If not, choose Help me calculate it and enter the width, height, and quantity of your doors and windows. The calculator will work out the total opening area for you.

For small openings, you may choose not to deduct them, as some extra paint can be useful for touch-ups, waste, or future repairs.

Paint Calculator Example

Imagine a room that is 5 metres long, 4 metres wide, and 2.4 metres high. The total wall area is 43.2 square metres.

Suppose the room has one door measuring 0.9 m × 2.1 m and two windows measuring 1.2 m × 1.2 m each. You can choose Help me calculate it and enter these measurements, or choose I know the total area if you already know the combined opening area.

After subtracting the doors and windows, the calculator determines the paintable area. With two coats selected, it then calculates the total coverage required.

If the paint covers 10 square metres per litre, the calculator estimates the amount of paint required. If you also enter a paint container size, it will round up to the number of containers needed.

Frequently Asked Questions

How much paint do I need?

The amount of paint you need depends on the paintable surface area, number of coats, and the coverage rate of your chosen paint.

How do I calculate paint for a whole room?

Choose "A whole room" and enter the room length, room width, and wall height. The calculator uses the room perimeter to calculate the total wall area.

Does the calculator subtract doors and windows?

Yes. If you already know the combined area of your doors and windows, choose I know the total area and enter it directly. Otherwise, choose Help me calculate it and enter the width, height, and quantity of your doors and windows. The calculator will subtract the total opening area from the wall area.

What paint coverage should I use?

Use the coverage rate provided by the paint manufacturer whenever possible. Coverage can vary between products and surfaces.

Does this calculator include multiple coats?

Yes. Enter the number of coats you plan to apply, and the calculator includes them in the estimated paint requirement.

How many paint containers should I buy?

Enter the container size you plan to purchase. The calculator will round up to the next full container so that the estimated paint requirement is covered.

Important Note

This paint calculator provides an estimate only. Actual paint requirements can vary depending on surface condition, texture, porosity, application method, paint formulation, colour change, and manufacturer specifications.

Always check the paint manufacturer's coverage and application instructions before purchasing paint.