PPF thickness is quoted in mil in the US and in µm (micrometers, or microns) almost everywhere else. The conversion is exact. The confusion comes from what is being measured.
The units
- 1 mil = 0.001 inch = 25.4 µm. This is exact, by definition of the inch.
- 1 µm = 0.001 mm. One micrometer is a thousandth of a millimeter.
- A mil is not a millimeter. 1 mm is 1,000 µm, or about 39.37 mil.
To convert:
- µm = mil × 25.4
- mil = µm ÷ 25.4
Conversion table
| mil | µm |
|---|---|
| 6.0 | 152.4 |
| 6.5 | 165.1 |
| 7.0 | 177.8 |
| 7.5 | 190.5 |
| 8.0 | 203.2 |
| 8.5 | 215.9 |
| 9.0 | 228.6 |
| 10.0 | 254.0 |
And the other way:
| µm | mil |
|---|---|
| 150 | 5.91 |
| 175 | 6.89 |
| 200 | 7.87 |
| 225 | 8.86 |
| 250 | 9.84 |
Data sheets often round. A film listed as “7.5 mil” may show “190 µm” on its European data sheet. That is the same film, rounded from 190.5 µm.
Same number, different film
Thickness can be measured with or without some of the layers:
- Film only: the base film plus the top coat. This is the usual headline number.
- Film plus adhesive: a larger number for the same product.
- Including the release liner: larger again. The liner is peeled off at install, so it adds nothing to the protection.
Before you compare two films, check which layers each data sheet includes. A “higher” number may just include more layers. Many data sheets also give a tolerance (±). A difference smaller than the tolerance is not a real difference.
Is thicker better?
Not on its own. Thickness is a trade-off. More material can mean more resistance to stone chips, but it also makes the film stiffer to stretch around deep curves and recesses. The right thickness depends on the panel and the job, so compare thickness together with elongation, top coat and warranty, not alone.
How we publish thickness
Every SHIELD product page shows thickness in µm and mil side by side, taken from the manufacturer’s data sheet, with a note on which layers are included. Until the data sheet is on file, the page says the value is pending instead of showing a guess.