Paint Calculator

Created by Bogna Szyk
Reviewed by Steven Wooding and Jack Bowater
Last updated: Mar 24, 2022

Whether you are planning to repaint your bedroom or are going to paint all the rooms in your brand-new house, this interior paint calculator is here to help you determine how much paint you need. You will be able to find the paint estimation based on the number of openings or the number of coats of paint. You can also calculate the final cost of paint required!

How much paint do I need?

You will have to input some raw data into the paint calculator. It includes:

  • Room dimensions — You need to type in the length, width, and height of the room you are going to paint. If your room has a different shape than a rectangular cuboid, you can also input the surface area directly into the paint estimator. The value calculated automatically takes into account only the walls.
  • Doors — You can leave the default dimensions of a door or customize them to fit your needs. Once you type in the number of doors in the room, the paint calculator will find their total area automatically.
  • Windows — Again, you can choose the default dimensions or type in custom ones. If you have windows of different sizes in your room, you can also calculate the total area manually and input this value into the appropriate box.
  • Number of coats — By default, our calculator finds the amount of paint required for one layer, but you can input the number of coats you plan to use yourself.
  • Paint efficiency — This number should be written on the paint can, expressed in m²/l or ft²/l.
  • Cost per unit — Optionally, you can input the cost of a unit of paint (cost per liter or per gallon). The paint calculator will automatically find the total cost of paint.

Is the paint estimation accurate?

Obviously, it won't be a hundred percent accurate. If the surface is porous or rough, it will require additional paint — up to 20%. Similarly, complicated fittings require extra paint.

You also need to add some paint — up to 30% — if you are painting a surface for the very first time, as you need to prepare the wall.

Note that our interior paint calculator does not include the ceiling, so, if you want to include it, you need to plan some extra paint for that.

Lastly, you may want to compare painting your room with using wallpaper instead. You can achieve this with our handy wallpaper calculator.

What about the floor?

You're not going to paint your floor, are you? Calculate the square footage of your floor and then decide on the finishing layer — is it going to be wood panels, or maybe some tiles or epoxy resin?

Bogna Szyk
Room length
ft
Room width
ft
Room height
ft
Room surface area
ft²
Doors
Door height
in
Door width
in
Number of doors
Total doors area
ft²
Windows
Windows height
in
Windows width
in
Number of windows
Total windows area
ft²
Amount of paint
Net room area
ft²
Number of coats
Paint efficiency
ft²
/l
Amount of paint
US gal
Cost per unit
$/
US gal
Total cost
$
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