Paint Calculator
About Paint Calculation
The calculator estimates paint consumption for walls based on the paintable area, number of coats, substrate type, and application method. It is suitable for a preliminary estimate of paint volume before renovating an apartment, house, office, or a single wall. If needed, the primer is also calculated separately for one coat over the same area used for painting.
Reference points and recommendations
The area used as the basis of the calculation
Base wall area. First, the calculator determines the total wall area S in m2. For a rectangular room, the formula is S = 2 × (A + B) × H, where A and B are the room length and width in m, and H is the wall height in m.
Single wall. If the calculation is for one wall, the area is determined as S = L × H, where L is the wall length in m and H is its height in m.
Known area. If the area is already known, the calculator accepts it directly in m2 without additional geometric calculations.
How windows and doors are subtracted
Openings. The area of windows and doors can be entered directly as a total value in m2 or calculated from dimensions. For windows, the formula is Sw = n × b × h, where n is the quantity, b is the width in m, and h is the height in m. The same principle is used for doors.
Paintable area. After that, the calculator determines the net paintable area using the formula Spaint = S - Sopen. If the opening area turns out to be greater than the wall area, the result does not go below zero and is taken as 0 m2.
How paint is calculated for the first and subsequent coats
Standard consumption. The calculation is based on the entered paint consumption in ml/m2. This is the consumption for one coat on a conditionally standard surface, after which it is adjusted by coefficients for the substrate, application method, and painting mode.
First coat. For the first coat, the paint volume is determined by the formula V1 = Spaint × q × kmode1 × ksurface × kmethod, where q is the paint consumption in ml/m2. The obtained value is converted to litres by dividing by 1000.
All coats. For the total volume, the calculator adds the consumption of the first coat and the consumption of the following coats. The formula is V = V1 + (N - 1) × Spaint × q × kmodeN × ksurface × kmethod, where N is the number of coats from 1 to 3.
Coefficients used in the calculation
Application conditions. For first-time painting, the calculator increases the consumption of the first coat by a coefficient of 1.10. For the second and third coats, 1.00 is used. For repainting, all coats are calculated with a coefficient of 1.00.
Surface type. For a smooth prepared surface, the coefficient is 1.00. For plaster or concrete, it is 1.10, for a textured surface with relief it is 1.20, for a rough texture it is 1.35, and for a porous substrate such as aerated concrete it is 1.50.
Application method. For a roller, the coefficient is 1.00, for a brush it is 1.05, and for spray application it is 1.15. This allows the calculator to account for differences in material losses and paint distribution over the surface.
- A common reference point for interior walls is
2coats. - For high-hiding paints on an even surface, a typical consumption is often about
100-180ml/m2 per coat. - For more absorbent or textured surfaces, the consumption often increases to
150-250ml/m2 per coat. - If the manufacturer states the spreading rate in m2/l, it can be converted using the formula
1000 ÷ (m2/l) = ml/m2.
How primer is calculated
Primer. If this mode is enabled, the calculator determines the primer volume for one coat only. The formula used is Vprimer = Spaint × qprimer × ksurface × kmethod, where qprimer is the entered primer consumption in ml/m2.
Calculation principle. The increased first-time painting coefficient 1.10 is not applied to primer. The calculation takes into account only the area, the absorbency of the substrate, and the application method, after which the result is converted from ml to litres.
How the result should be interpreted
Total volume. The result shows the calculated quantity of paint in litres for the selected conditions. In practice, the material is usually purchased with a small reserve for cutting-in, local losses, differences in texture, and possible deviation of the actual consumption from the stated value.
Related European standards. For assessing the characteristics of interior water-borne coatings, the standard EN 13300 "Paints and varnishes. Water-borne coating materials and coating systems for interior walls and ceilings. Classification" is often used. For wet scrub resistance, EN ISO 11998 is applied, and for hiding power, EN ISO 6504-3 is often used as a reference. Against the background of these documents, the calculator solves a practical task - converting area and application conditions into an estimated paint volume.
FAQs
Why is the consumption for the first coat higher than for the following coats?
For first-time painting, the calculator applies a coefficient of 1.10 to the first coat because the substrate usually absorbs more material and the first pass forms the main coverage of the surface. For the following coats, a coefficient of 1.00 is used because they are applied over a surface that is already partially sealed.
Why does the same wall area produce different paint consumption values?
The result depends not only on the wall area but also on the texture of the substrate, its porosity, and the application method. Because of this, paint consumption for the same area can differ noticeably between a smooth filled wall and porous aerated concrete.
Should windows and doors be subtracted from the area?
If the goal is a more accurate estimate for purchasing materials, it is better to subtract the opening area. This is especially useful for large windows, several doors, or when the paint calculator is used for a small room where the share of unpainted area is noticeable.
Can the calculator be used for a ceiling?
The logic of calculating paint consumption by area and number of coats remains the same, so the principle itself is also suitable for ceilings. However, it is better to make a separate calculation for a ceiling because the area, application method, and actual consumption often differ from walls.
Why can the calculator result differ from the actual consumption on site?
The stated paint consumption is usually given for specific test conditions and a prepared substrate. On a real project, consumption is affected by temperature, surface absorbency, preparation quality, application technique, and the actual coat thickness, so the paint consumption calculation should be treated as an engineering reference for purchasing rather than as an absolutely fixed value.