Paint calculator
Mils to microns converter
Convert a paint gauge reading between mils and micrometers. Paste several readings from one panel to see the lowest, highest, average, and spread.
Convert one value
Type in either boxCheck one panel's readings
Results update as you typeExample readings · invented values, not typical readings
5 readings. Average 112.6 µm, spread 36 µm.
Against the typical factory range: 1 below 100 µm, 4 inside, 0 above 180 µm. A reading outside the range is a reason to look closer, not proof of a repaint or of thin clear coat. DeFelsko says there is no single right thickness for every car.
A wide spread on one panel can come from a repair, filler, a thin area, or a bad reading. Measure again at the same points before you decide anything. This tool does not tell you if a panel is safe to polish.
What is a mil?
A mil is one thousandth of an inch: 0.001 inch. It is not a millimeter. Some paint gauges show mils. Others show micrometers (µm), also called microns, and many can switch between the two. A micrometer is one thousandth of a millimeter.
NIST lists 1 mil as exactly 0.001 inch, exactly 0.0254 millimeter, and exactly 25.4 micrometers (NIST Handbook 44 (2024), Appendix C: General Tables of Units of Measurement, accessed October 17, 2026).
The formulas
- Microns = mils × 25.4
- Mils = microns ÷ 25.4
- Inches = mils ÷ 1,000
- Millimeters = microns ÷ 1,000
Example: 5 mils × 25.4 = 127 µm. In the other direction, 120 µm ÷ 25.4 = 4.724 mils, rounded. The converter rounds mils to 3 decimal places and µm to 2. A gauge itself usually shows fewer digits than that.
Mils to microns chart
| Mils | Micrometers (µm) |
|---|---|
| 0.5 mils | 12.7 µm |
| 1 mil | 25.4 µm |
| 1.5 mils | 38.1 µm |
| 2 mils | 50.8 µm |
| 2.5 mils | 63.5 µm |
| 3 mils | 76.2 µm |
| 4 mils | 101.6 µm |
| 5 mils | 127 µm |
| 6 mils | 152.4 µm |
| 7 mils | 177.8 µm |
| 8 mils | 203.2 µm |
| 10 mils | 254 µm |
| 12 mils | 304.8 µm |
| 15 mils | 381 µm |
| 20 mils | 508 µm |
Microns to mils chart
| Micrometers (µm) | Mils |
|---|---|
| 10 µm | 0.394 mils |
| 25 µm | 0.984 mils |
| 35 µm | 1.378 mils |
| 50 µm | 1.969 mils |
| 75 µm | 2.953 mils |
| 100 µm | 3.937 mils |
| 125 µm | 4.921 mils |
| 150 µm | 5.906 mils |
| 180 µm | 7.087 mils |
| 200 µm | 7.874 mils |
| 250 µm | 9.843 mils |
| 300 µm | 11.811 mils |
| 400 µm | 15.748 mils |
| 500 µm | 19.685 mils |
Typical automotive paint thickness
These are typical figures from a gauge maker and from one car maker's research group. They are not limits, and they are not a safety guarantee. Paint thickness changes with the maker, the model, the panel, and the color. DeFelsko says there is no absolute target value and no “right” thickness.
| Layer or area | Typical, µm | Same in mils | Source |
|---|---|---|---|
| Total factory paint, most vehicles | 100–180 µm | 4–7 mils (source) 3.94–7.09 mils exact from µm | DeFelsko |
| Total factory paint, thin areas such as some roofs DeFelsko says some vehicles may have only this much on the roof. | 75 µm | 3 mils (source) 2.95 mils exact from µm | DeFelsko |
| Total factory paint, thick areas such as some SUV rocker panels DeFelsko says some SUVs may have this much on the rocker panels. | 430 µm | 17 mils (source) 16.93 mils exact from µm | DeFelsko |
| Clear coat alone A metal-panel gauge cannot measure this layer by itself. It reads the total. | 35–50 µm | 1.5–2.0 mils (source) 1.38–1.97 mils exact from µm | DeFelsko |
| Clearcoat in one OEM example stack | 45 µm | 1.77 mils | Ford Research (2016) |
| Basecoat (color) in the same stack | 10–20 µm | 0.39–0.79 mils | Ford Research (2016) |
| Primer in the same stack | 25 µm | 0.98 mils | Ford Research (2016) |
| Electrocoat in the same stack | 20 µm | 0.79 mils | Ford Research (2016) |
| Phosphate in the same stack | 5 µm | 0.2 mils | Ford Research (2016) |
DeFelsko rounds its own mil and micron pairs. For example, it writes 4–7 mils as 100–180 µm. The exact conversion of 4–7 mils is 101.6–177.8 µm. The table keeps the source's figures and shows the exact conversion beside them.
The Ford layers are one example stack, not a figure for every Ford or every car. Added together, they come to 105–115 µm. That sum is our arithmetic, not a figure from the source.
Signs of a repaint
DeFelsko says readings thicker than the typical factory range are often a sign that the panel was repainted. Elcometer says a paint meter can find hidden rework, respray, impact damage, and filled body panels by measuring paint thickness. Neither source gives one number that proves a repaint. Compare each panel with the panels next to it on the same car, and measure again at the same points.
A low reading also needs a closer look. It can mean a thin factory area, a panel that has had paint removed, or a reading taken badly. A thickness number alone cannot tell you which.
What one reading can and cannot tell you
A magnetic or eddy-current gauge on a steel or aluminum panel reads the total paint above the metal. That total includes clear coat, color, primer, and anything else on the panel. It cannot show how much clear coat is left. DeFelsko gives clear coat alone as about 35–50 µm, but you cannot see that layer by itself with an ordinary metal-panel gauge.
That is why the tool takes several readings. One reading can be off because of dirt, a curved edge, or the probe angle. The average shows the general level on the panel. The spread, the highest reading minus the lowest, shows how even it is. A large spread is a reason to stop and find out why before you polish.
Read the paint thickness gauge guide to choose a gauge for the panel material, check it against a reference, and keep a reading record. Then see the conservative one-step polish guide for a careful first polish.
Questions
How many microns is 1 mil?
Exactly 25.4 micrometers. 1 mil is 0.001 inch, and 1 inch is exactly 25.4 millimeters.
Is a mil the same as a millimeter?
No. 1 millimeter is about 39.37 mils. If a reading of “4 mil” looks like 4 mm, the paint would be 4,000 µm thick, which is far more than any normal car paint.
Can I paste readings with commas as decimals, like 4,5?
No. The tool reads every comma as a break between two readings, so 4,5 becomes 4 and 5. Use a period for decimals: 4.5.
Is a panel safe to polish if its readings are in the typical range?
The tool cannot say that. A typical total does not show how much clear coat is left. Ask a qualified paint repairer about readings you cannot explain.
Sources
All sources accessed October 17, 2026.
- NIST Handbook 44 (2024), Appendix C: General Tables of Units of Measurement
- DeFelsko: How to Use Paint Thickness Gauges for Better Automotive Detailing
- Mark Nichols, Ford Research and Advanced Engineering: Paint Materials and Processes from an Automotive OEM Perspective (July 20, 2016), hosted by NIST
- Elcometer 311 Automotive Paint Meter product page