Paint quantity 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 needed depends 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- for painting new plasterwork, a watered down coat of paint is required as a primer. Water the paint down by mixing 60% paint to 40% water. This coat soaks into the new plaster, and form a key to subsequent full coats. If you apply undiluted paint to new plaster, it won’t soak into the plaster, and is likely to peel off.

Paint Quantity: Ceilings

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 are required, so ensure you have enough paint to cover 48 square metres in total.


Paint Quantity: Walls

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 is required, so get enough paint to cover 100 square metres.

REMEMBER- measure any windows or doors, to remove this from your measurement, which reduces the amount of paint required.



There are important differences between Professional trade paints and retail paints. Professional paints must 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 has differing levels of coverage. The recommended spreading rates of the paint usually is 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 paint quantity required are:

  • When painting over existing dark colours, and you require the finish to be in a pastel colour, it is 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.
  • When decorating in colours from the deep red or deep yellow spectrum, 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, omit the bulking agents, for example talcum powder, 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 on Residential Painting, check out our blog here.