How To Work Out How Much Paint You Need for Any Home Decorating Project

How much paint do I need for my project? How many coats of paint are needed? If you’re asking these questions, you’re not alone. Buy too little paint and you end up back and forth to purchase more. Buy too much and you end up with cans stacked up in the shed (although this could be useful for touch ups!) If only such thing as a paint calculator existed, eh? Well, you’re in luck, because we’re here to show you just how simple it can be to calculate the paint you need with just three easy steps, no guesstimates necessary. 

Step 1 - Measure up

First off, you need to grab a tape measure to work out the height and width of the surface you want to paint. Then, multiply the height and width together to get your square metre measurement. Subtract any windows and doors by using the same calculation method and deducting it from the total.

Step 2 - Calculate your coats

This is where we answer your how many coats of paint query. 

Step 3 - Divide and conquer

Finally, divide the number by the square metre per litre listed on your paint tin or in the online product information. And there you have it, you’ve worked out the amount of paint you need.

I’m already in-store, how much paint do I need?

Do not fret! If you don’t have the measurements of the space you’re painting to hand, but you need to purchase that paint, we’ve put together a handy paint estimator.

Roller Tester
Enough for a small patch on a wall

Interior Wood and Metal
A 750ml tin is perfect for a door or the skirting in a small room

Feature Wall
A 1 litre tin will be ideal to paint a 2.5m interior wall

Small Room
Around 2.5 litres would cover all walls in a 2m x 2m or equivalent room

Medium Room
You’ll need about 5 litres to cover all walls in a 4m x 4m or equivalent room 

How much Paint is needed ?

Formula for Paint Calculator

Overall room measurement​

Calculating the overall room measurement​

1. Width x height of walls = Overall room measurement

Overall door and window measurement

Calculating the overall door and window measurement​

2.  Width x height of doors and windows = Overall door and window measurement​

3.  Overall room measurement – Overall door and window measurement = Wall space to be painted​

4.  Wall space x 2 (for two coats) + a little for touch ups = Total​

5.  Total ¸ m²/l number on your paint tin = Number of liters of paint you need for your project​

These steps can also be used to calculate how much paint you need for ceilings and floors.​

Pick the perfect paint for your project with our essential guide to finishes.​