An indispensable step in the finishing work is the accurate planning of the cost of materials. The total cost of repair depends on the correctness of the calculations. Preparing an estimate will save time, resources and money.

## What should be taken into account when calculating

Not only people associated with the exact sciences should be careful and pedantic to determine the correct repair costs. Anyone who decides to change the interior in the apartment, should take seriously the calculation of the required materials. Leftovers do not find further use and, given the small shelf life in open containers, they are thrown away.

If you buy an insufficient amount of wall paint, it will then be difficult to match the shade. Not always the matching numbers, marking the color, guarantees an exact hit in the shade. The determining factor for the same shade is the batch number of the product.

On the cans they write all the necessary information about the method of use. Including the flow rate for painting 1 square meter of wall area is indicated. It is difficult to be guided by this data, because average figures are given, without the peculiarities of each repair.

When calculating the amount of paint for decorating, you must take into account a number of factors:

- the original color of the surface. If the wall is painted in a bright tone, the intended light shades will need to be put in several layers. And any shade will go well on a white color.
- the tool that will be used when working – a brush, roller or paint sprayer.
- the degree of smoothness of the walls. Porous and rough surfaces will require increased consumption.
- paint composition. Additional tinting can increase the amount of coverage required.

Careful study of all the details of applying paint to the walls will ensure a correct calculation and will save finances that are already spent in large quantities during repairs.

## What tools are needed

The amount of paint needed depends on the painting device with which layers are applied to the wall. Use one or more tools for this purpose:

- Brush – applies the composition in a thick layer with inevitable runs. The most costly way of painting with the maximum consumption of the finishing coat.
- Roller – reduces the time of painting work, so it is used for painting a large area. The paint is spent economically.
- Spray gun – distributes paint evenly over the entire wall surface and quickly applies a thin layer. Option for thrifty repairs.
- Sponge – used for painting finish coatings. Increases consumption because a thick coat is applied to the wall when painting decoratively.

Usually several types of tools are used in the painting work. This is due to the presence of corners, heating radiators and varieties of painting. All these nuances must be taken into account when calculating the amount of paint.

## Initial color and surface structure

The initial shade of the surfaces is of primary importance. White walls are enough to cover with one light layer in order to refresh the color or hide the translucent patterns of the base. If the choice is made on bright or dark tones, you will have to paint two or more times.

Hiding coefficient is the ability of the pigment to overlap the color of the base and make the differences between contrasting areas invisible when evenly painting.

The coefficient of hiding power is determined in grams of pigmented material required to cover one square meter of the surface in one layer. According to this characteristic, there are 4 classes. The smaller the number, the better the new shade will cover the previous coating. Accordingly, the consumption of finishing material for paint class 1 will be minimal.

A well-prepared surface will require less paint. If there is whitewash on the walls, it should be thoroughly washed off with plenty of water. Remains of old coatings, plaster, glue – all must be removed. The clean surface should be sanded and coated with a primer, which will save consumption.

If you do not treat the walls with a primer, the amount of product will increase significantly:

- on wood surfaces, up to 10 percent;
- not primed plaster – by 15 percent;
- on drywall – by 40 percent;

A lot of paint material will be needed to cover embossed wallpaper. Costs will increase twice as much, compared to treated concrete walls.

Standard is considered the consumption of paint in the range of 120-140 grams per 1 square meter of surface when painting in one layer. The lighter the shade, the less dense the consistency. Consumption in this case increases, because you have to paint several times.

## How to do the calculation yourself

To correctly calculate the amount of paint you need to know two parameters – the area to be painted and the consumption rate per 1 square meter. Determining the wall area is easy with a tape measure and simple mathematical formulas:

Measure the length (a) and width (b) of the room in meters and determine the perimeter (P) of the room using the formula P = (a+b) × 2.

2. Measure the height of the walls (h) or the distance from the floor to the paint line.

3. Calculate the area (S) to be painted according to the formula S = P × h.

4. 4. Take into account all door and window openings, calculate their total area and subtract from S the walls.

The resulting value is used to determine the required volume of material. To do this multiply the wall area without openings by the consumption rate indicated on the package.

Example:

Length of a room – 4.2 m

Width of the room: 3.4 m

Wall height from floor to ceiling: 2.6 m

Window aperture: 1.5 x 1.7 m

Doorway – 0.8 × 2.0 m

Consumption per square meter – 120 grams

P = (4.2 + 3.4) × 2 = 15.2

S = 15.2 × 2.6 = 39.52

S window = 1.5 × 1.7 = 2.55

S door = 0.8 × 2.0 = 1.6

39.52 – (2.55 + 1.6) = 35.37

120 × 35.37 = 4,244.4 grams or 4,244 kg

The walls of a room 3.4 m wide, 4.2 m long and 2.6 m high would need 4.2 kg of paint in a single coat.

## Consider the tolerances

For an accurate calculation additional parameters must be taken into account:

– The dry residue – the amount of substances remaining on the dried surface;

– Compound density – how much paint in 1 cubic centimeter;

– hiding power – the indicator of color overlap of the substrate.

To determine the actual consumption of paint, use the formula:

(hiding power / dry residue) × 100

The resulting value is multiplied by the wall area.

Example:

Area to be painted – 35 sq. m.

Hiding power – 130 grams per 1 sq. m.

Dry residue – 60%

(130 / 60) × 100 = 216.6 grams per sq.m.

216.6 × 35 = 7 581

To paint 35 square meters in one coat would require 7.6 kg.

As the amount of solid fillers in comparison with polymers increases, so does the density of the paint material. Compounds lose plasticity and add consumption. It is allowed to dilute products with special formulations, depending on the type of paint, to reduce the density.

For ease of calculation, it is recommended to reduce all values to common units of measurement. It will help to avoid gross errors in calculations and correctly determine the paint quantity.