A mil is one-thousandth of an inch, the standard U.S. unit for measuring coating thickness. It’s not a millimeter; a mil is much thinner. Floor coatings are often described by how many mils they build per coat and in total. In general, thicker systems hold up better to traffic and impacts.
What Mil Thickness Means for Your Floor Coating
A mil is one-thousandth of an inch, so the numbers add up fast. Floor coatings span a wide range. Epoxy flake systems alone run from about 10 to 250 mils, depending on how many layers go down and how heavy the duty is.
Think of mils like the thickness of a phone case. A thin skin looks the same as a rugged case on day one, but only one survives a drop. A thin, single-coat roll-on product, like many garage floor paints, can look fine at first but has less material to wear through.
Thicker isn’t automatically better, though. Surface prep, the right product, and a good topcoat matter just as much. A thick coat over a poorly prepped slab can still peel.
What to Ask Your Contractor About Mil Thickness
Mil numbers help most when comparing quotes. Ask:
- How many coats are in the system, and how thick is each one?
- What’s the total thickness once it’s cured?
- Is the topcoat thick enough to cover the flake or grit evenly?
For more on coating systems, see our guide to concrete floor coatings.
Mil Thickness FAQ
What does 1 mil thickness mean?
One mil is one-thousandth of an inch (0.001 inch). Coatings and plastic films are both measured in mils. It’s a different unit from a millimeter, which is much thicker.
Which is thicker, 4 mil or 6 mil?
Six mil is thicker. Higher mil numbers always mean a thicker layer, so a 20-mil coating has five times the material of a 4-mil coating.