How To Calculate Amount of Paint Required ? November 1, 2008
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If your project is small enough, like painting a grille, or touching-up a couple of nail holes, you never have to worry how much paint you would need to buy. Just purchase the smallest pack and you’ll still have some leftovers. When the projects get bigger, you would need to come up with a good estimate. Otherwise, you may end up with way too much, which can be quite costly, or too little, which can be equally costly especially if you have half a dozen workers having an unscheduled "tea-break" while you "top-up".
To calculate the amount of paint required for a particular project, you would need to known basically 2 pieces of information :
- the area to be painted and
- the coverage of the paint
How to calculate the area to be painted?
a) Walls - Multiply the length and height of the wall to get the area.
b) Room - Add up the areas of all the walls of the room
c) Doors - Multiply the breath and height of the door and double it (for painting on both sides)
d) Cylindrical Pipes - Measure the diameter and the length of the pipe and use the following formula:
Diameter x Length x 3.14
How do I obtain the coverage of the paint?
The coverage of the paint can be found on the product datasheet (also called technical datasheet or product specification). The way it is presented varies with company. Below is an example of Nippon emulsion paint:
The above shows that the theoretical coverage of this paint is 13 sq m / litre at 30 micron DFT (dry film thickness). In other words, one litre of paint can cover 13 square metres if painted at a dry film thickness of 30 microns.
Putting It All Together
Dividing the area to be painted by the coverage, we will arrive at an amount of paint required in litres. For example, if the area of a room is 48 sq metres and the coverage is 13 sq metres per litre, then the amount of paint needed is 48/13 or 3.7 litres. Add 20% loss factor and you’ll arrive at 4.44 litres. Remember that this is for one coat. Double it if you need to paint 2 coats.
Some Tips and Shortcuts
1) In our local context, a HDB room usually requires one can of 5-litre emulsion paint. Living rooms of 4-rooms and above usually need 2 cans.
2) If you do not have access to datasheets, use 8-10 sq m per litre for emulsion paint and 12 - 14 sq m per litre for oil-based paint. This does not work for industrial paints which can vary quite a lot.
3) Rockstone surfaces would require more paint and may need up to 50% more for rougher grains.
4) If the area to be painted is in square feet, multiply it by 0.093 to arrive at the equivalent in square metres.
Hope this post helps you in calculating the amount of paint needed to get that paint job done. However, amount calculated can still vary depending on painting technique, equipment used and surface profile.
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Hi,
I wanted to know about industrial paint system,which i have to paint for steel structurals.Please let me know how to calculate the amout of paint required if i have a area in square meters(8500 square meter) & DFT may be 40,50 microns 2coat systems.
How much wastage factor i have to consider.
Ashok,
We normally add a 20% loss factor.
You would need to have the practical coverage for the paint you are using and this can be found on the technical datasheet for the paint. If you give me this number and the DFT of the paint, I can show you the calculation. Regards.
could u give me step by step infomation on the question below
question how much paint would be required to paint the external surface of a 4 meter diameter circular cylinder standing 7 meters in height? the flat circular top of the cylinder must also be painted. the paint to be used is solvent free and the surface of the cylinder has been wire brushed. the dft required is 130um
Kenneth,
Need to know the coverage of the paint. Different types of paint have different coverage and this may vary quite a bit. The coverage information is usually found on the product technical datasheet.
Regards.