Finishing worked example

Coating Thickness Variation with minimum film reading of 4 mils: a worked example

Here is what the math looks like when conditions slip. We hold every other input steady and drop minimum film reading to 4 mils, then walk the calculation through step by step. Calculate film thickness spread and variation from minimum, maximum, and average readings.

The inputs for this scenario

  • Minimum film reading: 4 mils (the input this scenario stresses; the baseline uses 8)
  • Maximum film reading: 12 mils (held at the documented default)
  • Average film reading: 10 mils (held at the documented default)

Working through the calculation

  • The calculation starts from the formula this tool documents: Spread = maximum - minimum.
  • Variation works out to 80 % variation at these inputs, and this is the headline figure for the scenario.
  • Spread works out to 8 value at these inputs.
  • Minimum works out to 4 value at these inputs.
  • Maximum works out to 12 value at these inputs.

How this compares with the baseline

  • Against the tool's baseline example, where minimum film reading sits at 8 mils and the headline result is 40 % variation, this scenario comes in 100% above the baseline at 80 % variation.
  • The practical read: the gap between this scenario and the baseline is entirely attributable to minimum film reading, so recovering it is worth quantifying in dollars before considering equipment or staffing changes. It uses only three numbers, so it can't tell you where on the part the extremes occurred or whether the distribution is skewed; a full reading map gives a truer picture.

Results at a glance

  • Variation: 80 % variation (headline result)
  • Spread: 8 value
  • Minimum: 4 value
  • Maximum: 12 value

Run it with your numbers

  • To rerun this with your own numbers, open the live Coating Thickness Variation calculator, set minimum film reading to your actual value, and adjust the remaining inputs to match your operation.

Last reviewed 2026-05-12.