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Powder coating of steel structures
Paint and powder coating consumption calculator: area, coats, loss
The calculator works out how much liquid paint (primer, intermediate coat, enamel) or powder coating is needed for a given area of steel. For liquid paint it takes into account dry film thickness, volume solids, application loss and pack size; for powder, the film thickness, powder density and transfer efficiency. The result can be saved to Excel or printed.
Contents
Paint consumption calculator
Enter the surface area and choose the coating method. For liquid paint set the coats: dry film thickness and volume solids from the material’s data sheet. The numbers in the fields are an example, not a manufacturer’s recommendation.
This is an approximate calculation. It does not account for surface roughness, welds, corners and complex geometry, thinning, what stays in containers and an allowance for repairs. The real consumption is set by the material data sheet and a trial application.
Request a calculationHow to use it
- area: from the shop drawing specification, from the metal weight calculator (the «surface area» line) or from a drawing; for pipes and sections the outside is painted, sometimes the inside as well;
- liquid paint: for each coat the dry film thickness (DFT) and the volume solids (VS) are taken from the data sheet; enter the density if you need the mass;
- loss: enter your own or choose the application method; the values by method are approximate;
- pack size: the calculator rounds the number of containers up for each coat separately;
- powder: the film thickness, powder density and transfer efficiency are set by the applicator or by the powder data sheet.
Examples
The examples are conditional, their values are taken for illustration. In a project they are replaced by the data sheet of the chosen material.
| Conditions | Theoretical consumption | With loss | Containers |
|---|---|---|---|
| 100 m², airless spray (30 %), 2 coats of 60 µm, VS 60 % and 55 % | 10.0 l + 10.9 l | 29.9 l | 1 + 1 of 20 l |
| 50 m², roller (20 %), 1 coat of 80 µm, VS 70 % | 5.7 l | 7.1 l | 1 of 10 l |
| 250 m², airless spray (30 %), 3 coats of 75 / 100 / 50 µm, VS 60 / 65 / 50 % | 31.3 l + 38.5 l + 25.0 l = 94.7 l | 135.3 l | 3 + 3 + 2 of 20 l |
| 100 m², powder 80 µm, density 1.5 g/cm³, transfer efficiency 65 % | 12.0 kg | 18.5 kg | — |
| 30 m², powder 100 µm, density 1.4 g/cm³, transfer efficiency 60 % | 4.2 kg | 7.0 kg | — |
How it is calculated
Liquid paint. Volume solids show what share of the liquid stays as a film after drying. The volume needed for a coat is V = S · DFT / (10 · VS), where S is in m², DFT in µm, VS in percent and V in litres. For example, 100 m² at 60 µm and VS 60 % need 10 l, or 10 m²/l. The practical consumption is higher: Vp = V / (1 − Z/100), where Z is the application loss (overspray, what stays in hoses and containers). The number of containers is Vp divided by the pack size, rounded up.
Powder coating. The mass of powder for a film is M = S · H · ρ / 1000, where H is in µm, ρ in g/cm³ and M in kg. The practical mass is Mp = M / (TE/100), where TE is the transfer efficiency, the share of powder that stays on the product. In some systems the powder that did not stay is returned to the cycle; the calculation shows it as consumption without return.
What the calculator does not take into account
- surface roughness: after abrasive blasting, and on zinc, the consumption is higher than calculated;
- complex geometry: welds, corners, holes, brackets and thin sections increase the consumption;
- thinning with solvent: the calculator works with the material as delivered, not at working viscosity;
- what stays in containers and an allowance for repairs and touching up;
- application conditions: temperature, humidity, time between coats, compatibility of coats. These are set by the data sheet.
What to send for a calculation
To calculate the cost of coating within an order we need drawings or a specification (area or mass), the coating requirements (system, thickness, RAL colour) and the service conditions. More on choosing a coating: how to choose protection for steel, powder coating, powder coating price. The area of a product comes from the metal weight calculator.
Updated:
Paint consumption calculator: frequently asked questions
Why is the real paint consumption higher than the calculated one?
The calculation gives a theoretical value for a flat surface. In practice some paint is lost: overspray, what stays in hoses and containers. That is why the calculator shows the consumption with loss separately. Roughness and complex geometry increase it further.
Where do I find volume solids and film thickness?
In the paint manufacturer’s data sheet. It is one of the main parameters of the material. The numbers in the calculator fields are an example, not the values of any particular paint.
Can I calculate from the mass of the steel instead of the area?
The calculator works with the area. The area of a product comes from the metal weight calculator (the «surface area» line) or from the shop drawing specification.
Does the calculator give the cost of coating?
No. It gives only the material consumption. The cost depends on the coating system, surface preparation and volume, and is calculated from drawings.
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