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Coating coverage calculator

Work out how much coating to order: area, dry film thickness, volume solids, losses and coats. Metric and imperial, formula shown.

Unit system

By volume, not by weight. Read it on the TDS.

Overspray, profile, mixing. Typically 20–40% on site.

Results

Theoretical volume

— L

Practical volume

— L

Containers

—

Practical spread rate

— m²/L

Formula used

practical volume = (area × total DFT) ÷ (volume solids × 10) × (1 + losses)

Area in m², DFT in µm, volume solids in %, result in litres. In imperial units, conversion happens before the calculation, never after: converting at each step would drift the rounding.

Variables

Area
Actual developed area to be coated. An I-beam develops far more surface than its footprint.
DFT
Target dry film thickness per coat, in micrometres. What the gauge reads after cure, not the wet film.
Volume solids
Share of product remaining on the surface once solvents evaporate. By volume, never by weight — the gap between the two is significant and the confusion is common.
Loss factor
Overspray, absorption into the anchor profile, mixing residue, purging. Commonly 20–40% on site, more on complex shapes or in wind.
Coats
Total thickness is multiplied accordingly.

Method and source

Theoretical spread rate follows directly from volume solids and target thickness. This is the same relationship manufacturers apply when publishing theoretical coverage on their data sheets, and it is described in ASTM D5201 (calculating formulation physical constants of paints and coatings). The loss factor, by contrast, is not standardised: it is a site parameter.

Limits of use

  • The result is a basis for ordering, not a guaranteed spread rate. Real losses depend on geometry, application method and conditions on the day.
  • The calculation assumes uniform thickness. In practice, distribution is uneven: allow the margin your specification requires at the thinnest point.
  • Volume solids vary batch to batch with some manufacturers. Use the figure from the exact product TDS, with its date.
  • Porous or heavily profiled surfaces consume more on the first coat. This calculator does not model that effect.

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Maintenance Blueprint, « Coating coverage calculator », maintenanceblueprint.com/en/tools/coating-coverage/