Material, choice of color, protection solutions… when carrying out painting work, there are a multitude of elements to consider. One of the key points of the project concerns the amount of paint needed. A quick calculation will prevent any form of waste or conversely, will avoid running out of paint to complete the work.

## Determine the area of the room to be repainted

The first step in the calculation to have a precise idea of the cans of paint to buy is to know the total surface to be repainted. In this context, it will first be necessary to determine the perimeter of the room. Use a tape measure to measure the length and width. Then do the following calculation: (length+width) x 2. In a bedroom with a length of 4 meters and a width of 3 meters, you will obtain a perimeter of 14 meters according to the formula (4+3 ) x 2 = 14. Now that you know the perimeter, use the result obtained to determine the area in m² of the room. The formula is to multiply the perimeter with the height of the walls. So, if the room is 2.5 meters high, you will get 14 x 2.5 = 35m².

Note that it is possible to make the calculations even more precise by taking into account windows and doors to be sure not to waste paint. If you do not want to touch these surfaces, you will have to subtract the surface of the openings from the surface of the walls. Clearly, apply the following calculation: wall area – (height x width of windows). If the windows are 2 m high and 1 m wide, you will get: 35 – (2×1) = 33m².

## How much paint needed?

Now that the hard part is done, it is now necessary to calculate the quantity of paint necessary. Attention, a very important detail to take into account when choosing the desired paint is the type of performance offered. In principle, the yield per liter is systematically indicated on the paint can. It is accepted that a quality product has a yield of 6 to 7m² per liter of paint. This figure can reach 12m² if the paint is very opaque. This opacity depends on the level of titanium contained in the paint. The “monolayers” are also the most covering.

In any case, to know the number of pots to buy, divide the surface to be painted by the yield of the paint and multiply the whole by the number of coats (which must be at least two). Clearly, if the paint offers a yield of 12m²/litre, you will obtain (33/12) x 2 = 5.5 liters of paint. On the market, you will find pots of 0.5, 2, 5 or even 10 liters.

Do not forget to take the ceiling into account. The calculation is simple. First multiply the length and width of the ceiling then divide the result by the paint yield and then multiply by the number of coats desired. This gives: ((4×3)/12) x 2 = 2 liters.