Paint is sold in various container sizes. The most common sizes are- 1 litre, 2.5 litres, 5 litres, 10 litres. Some paint manufactures package paints in 500 ml (half a litre), 3 litres, 7.5 litres, 15 litres.

The amount of paint you will need will depend on the porosity of the substrate, and how many coats you require to achieve full opacity. One coat of paint is rarely sufficient to achieve a good finish, unless it is the same colour. REMEMBER- if painting new plasterwork, a watered down coat of paint will be required as a primer. Water the paint down by mixing 60% paint to 40% water. This coat will soak into the new plaster, and form a key to subsequent full coats. If you apply undiluted paint to new plaster, it will not soak into the plaster, and is likely to peel off.


Measure the length and width of the floor area of the room, and multiply the two measurements. For example, if the room is 4 metres wide, and 6 metres long, 4 x 6 = 24 square metres. 2 coats will be required, so you will need enough paint to cover 48 square metres in total.



Measure the length of all walls of the room, and add them together. Then measure the height of the room, and multiply the two measurements. For example, if the room is 4 metres wide, and 6 metres long the total measurement will be 20 metres. Multiply this by the height of the room, say 2.5 metres, 20 x 2.5 = 50 square metres. 2 coats will be required, so you will need enough paint to cover 100 square metres. REMEMBER- measure any windows or doors, to remove this from your measurement, which will reduce the amount of paint required.



Need a little help with paint quantity?



There are important differences between Professional trade paints and retail paints. Professional paints need to be more durable and versatile to meet the needs of professional decorators and their clients.

  • Trade paints cover better and spread further than retail paints, even after thinning. For example: Retail Dulux Vinyl matt emulsion will cover 13sqm per litre. Trade Dulux Vinyl matt emulsion will cover 17sqm per litre. So 5 litres of Retail paint will cover 65sqm- one coat, and 5 litres of Trade paint will cover 85sqm- one coat.
  • Trade paints are consistently tested to ensure they offer the high standards required and relied on by professional users and their clients.
  • Trade paints are available in larger, more economical quantities than Retail paints.
  • Professional decorators will usually have opened Trade accounts with their main suppliers, and negotiated good price deals with them to ensure they can offer their clients more value for money.

Different types and brands of paint will have differing levels of coverage. The recommended spreading rates of the paint will usually be identified on the container. Good brands will also have a website, where you can access the data and relevant information for each type of paint.

Other important factors to consider when calculating the amount of paint required are:

  • If you are painting over existing dark colours, and require the finish to be in a pastel colour, it would be necessary to allow for 3 coats instead of 2. Applying a base colour of white could also be considered (as white emulsion is usually cheaper than tinted emulsion) prior to the application of the 2 coats of the required colour.
  • If you are looking to decorate in colours from the deep red or deep yellow spectrum, you may need to consider allowing for 1-2 more coats to achieve full opacity. This is due to the pigments being used will need to mixed into clearer bases to achieve the required deep colour.

Important Note

Paint has approximate 4 main components: Bulking agents, binders, liquid and pigments. Therefore, the bulking agents, for example talcum powder, will need to be omitted from the paint base if deep red and yellow pigments are used.

Wall 2 Wall Decorating are professional painters who can help you calculate the quantity of paint needed or offer assistance if you decide not to do it yourself. More information onĀ Residential Painting