roller with grey paint

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

How much paint do I need? Let Dulux show you how to calculate your paint coverage. Estimate the paint needed for woodwork, feature walls and any size room.


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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. 

dulux woman painting

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.

dulux paint brush

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 

paint roller emerald glade

How much Paint is needed ?



3 Rooms

4 Rooms

5 Rooms

Bedroom (Each)

5 litre Can – Qty 1

5 litre Can – Qty 1

5 litre Can – Qty 1


5 litre Can – Qty 1

5 litre Can – Qty 2

5 litre Can – Qty 2

All Ceilings

5 litre Can – Qty 3

5 litre Can – Qty 3

5 litre Can – Qty 4

Formula of Paint Calculator

Ceiling Paint Calculator Per Square Feet: We consider a room of dimensions 10*20 feet and with a height of 7 feet, which contains 2 windows and 2 doors.

Step 1: Calculate the total area i.e 10*20=200 square feet

Step 2: Divide it with a standard number 350(i.e 1 gallon of paint per 350 square feet area). We get 200/350= 0.5 gallons of paint needed that ceiling area.

Wall Paint Calculator:

Step 1: Calculate the area (10+20+10+20)*7=420 square feet

Step 2: Calculate windows and doors area i.e 20*2+15*2=70 sqaure feet where windows is 15 feet wide and doors are 20 feet.

Step 3 Now substract unpainted area i.e 420-70=350 square feet.

Step 4: Divide that number by 350 i.e 350/350=1 gallon of paint needed to paint interiors od room.

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