How much paint do I need, and how do I calculate it?

If you are trying to estimate the amount of paint you need, you’ve come to the right place and I’ll do my best to help you work it out.  I will use one of our top selling natural paints as the example. I’m going to be using: Graphenstone Grafclean Premium – This top quality natural paint can be used on all walls and ceilings, and in all rooms in the house. A great all rounder, tough, washable and with a beautifully natural matte finish. I use this everywhere to be honest! If you are a painting over pre painted walls, you don’t really need a primer, so that’s one less thing to worry about!

How do I know how much coverage I’ll get from the paint?

Graphenstone Premium has a coverage of 10-16m2 per litre.

Why does it say 10 to 16, isn’t that quite a bit difference? Well, yes, it is really as it really does depend on your application, what you’re using to apply it, and just how careful and accurate you are! So I’ll just take an average here, and average it out at 14m2 per litre.  ALWAYS check the data sheet on the paint webpage to make sure you know what the ‘coverage’ is for that paint, as it does vary (some paints have better coverage than others depending on the formulation)

So, that means that 1L of paint will cover 14m2 of wall area.  (‘m2’ means ‘metres squared’)

How do I work out my wall area is so I know how much paint I need?

It is worked out as a simple calculation of the HEIGHT (in metres) multiplied by the WIDTH (in metres).

WALL HEIGHT x WALL WIDTH = Wall area in m2

Example: 2M x 7M  = 14 m2

Then divide the paint specified paint coverage by the m2 wall area.
So in this instance, we need enough paint for 14 m2 and our paint covers at 14m2, so we need just 1 litre of paint (per coat)
TOTAL WALL AREA (14m2) / PAINT COVERAGE (14m2) = 1 LITRE

Example Paint Area Calculation

My wall measures 2m high, and 7m wide, so this is HEIGHT (2m) multiplied by WIDTH (7m) = 14m2

So, I need enough paint to cover 14m2 of wall area. We know that for every litre of the Grafclean premium we can cover 14m2 so that means for our wall we just need 1L of paint per coat. We generally advise 2 coats of paint to cover well, so therefore you will need 2L of paint to cover your wall with two coats.

What about areas I’m not going to paint, such as for window and doors?

Well, I’ve not accounted for areas that you won’t actually be painting, so things like doors, windows, skirting boards etc. If you can can work out the rough area of these then you can subtract it from your needed coverage.

So let’s use the above example again, so our wall is 2m high and 7m wide, so we enough paint to cover 14 m2 of wall area. However, there is a door in this wall, so measuring the door it’s (for arguments sake) is 1m wide by 2m high, so 1m x 2m = 2m2. So we can subtract 2m2 from our 14m2 total wall area, so actually we now only need 12m2 worth of paint! When you’re calculating a room, you need to bear this is mind as it can save you quite a lot of paint!

How much paint do I need for this room?

Here’s a more detailed example of how much paint you need for a wall

Let’s work out a bigger example, using a real room with 4 walls and 2 doors, and 2 windows.

AREAS TO PAINT: (Wall measurements, ignore doors etc, we’ll get to that!)

  • Wall 1: HEIGHT 2m x WIDTH 3m = 6m2
  • Wall 2: HEIGHT 2m x WIDTH 3m = 6m2
  • Wall 3: HEIGHT 2m x WIDTH 3m = 6m2
  • Wall 4: HEIGHT 2m x WIDTH 3m = 6m2
  • Ceiling: WIDTH 3m x LENGTH 3m = 9m2

Total = 33 m2.

AREAS NOT TO PAINT: (Doors and windows)

  • Door 1: HEIGHT 2m x WIDTH 1m = 2m2
  • Door 2: HEIGHT 2m x WIDTH 1m = 2m2
  • Window 1: HEIGHT 1m x WIDTH 1m = 1m2
  • Window 2: HEIGHT 1m x WIDTH 1m = 1m2

Total = 6m2

So, it’ll be: AREAS TO PAINT subtract the AREAS NOT TO PAINT

33m2 – 6m2 = 27m2

So we need enough paint to cover 27m2, so how do we work out how much paint wee actually need to paint the room? As we know, the coverage of this paint is 14m2per Litre. So we divide the amount of area we need to paint by the coverage of the actual paint per litre and we’re there!
So in this room example: 27 divided by 14 = 1.9

So we need just 1.9 litres of paint to paint this entire room in a single coat. So if we round this up to 2L of paint, then if we want 2 coats in total we now need 4L of paint in total to paint the entire room.

Common Questions

General Painting