Convert Micrometres per Year to Mils per Year (µm/y to mpy)
1 micrometre per year (µm/y) = 0.03937007874 mils per year (mpy). 1 mpy = 25.4 µm/y. Example: 25 µm/y = 25 × 0.03937007874 = 0.9842519685 mpy.
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1 µm/y = 0.03937007874 mpy
Type in either box. Scientific notation works: 1.5e-3.
Converting a list? Use the bulk micrometre per year to mil per year converter to paste a column from Excel.
How to Convert Micrometre per Year to Mil per Year
- 1 µm/y = 0.03937007874 mpy
- 1 mpy = 25.4 µm/y
- Example: convert 25 µm/y to mpy: 25 µm/y = 25 × 0.03937007874 mpy = 0.9842519685 mpy
Formula
mpy = µm/y × 0.03937007874016
or mpy = µm/y ÷ 25.4
Derivation from SI units:
- 1 µm/y = 0.001 mm/y
- 1 mpy = 0.001 in per year = 0.0254 mm/y (exact)
- 1 µm/y = 0.001 mm/y ÷ 0.0254 mm/y per mpy = 0.03937007874016 mpy
Both units are defined exactly, so the factor is exact. Micrometre per Year definition: micrometre per year; Mil per Year definition: mil per year.
Worked examples
- A zinc corrosion rate of 25 µm/y is 0.9842519685 mpy.
25 µm/y × 0.03937007874 = 0.9842519685 mpy - Carbon steel at 50 µm/y is 1.968503937 mpy.
50 µm/y × 0.03937007874 = 1.968503937 mpy
Micrometre per Year to Mil per Year conversion table
| Micrometres per Year (µm/y) | Mils per Year (mpy) |
|---|---|
| 0.1 µm/y | 0.003937007874 mpy |
| 1 µm/y | 0.03937007874 mpy |
| 2 µm/y | 0.07874015748 mpy |
| 5 µm/y | 0.1968503937 mpy |
| 10 µm/y | 0.3937007874 mpy |
| 25 µm/y | 0.9842519685 mpy |
| 50 µm/y | 1.968503937 mpy |
| 80 µm/y | 3.149606299 mpy |
| 100 µm/y | 3.937007874 mpy |
| 200 µm/y | 7.874015748 mpy |
Where it's used
Atmospheric corrosion rates in µm/y (ISO 9223 categories) are converted to mpy for US specifications and coating-life estimates. Divide by 25.4.
Micrometre per Year to other corrosion rate units
| Conversion | 1 µm/y equals |
|---|---|
| micrometre per year to mil per year | 0.03937007874 mpy |
| micrometre per year to millimetre per year | 0.001 mm/y |
| micrometre per year to inch per year | 0.00003937007874 ipy |
Frequently asked questions
How many mpy is 25.4 µm/y?
Exactly 1 mpy.
How many mils per year are in 1 micrometre per year?
1 µm/y = 0.03937007874 mpy.
How do I convert micrometres per year to mils per year?
Multiply the value in µm/y by 0.03937007874, or divide it by 25.4. For example, 25 µm/y × 0.03937007874 = 0.9842519685 mpy.
Is the µm/y to mpy conversion exact?
Yes. Both units are defined exactly, so the ratio is exact; its decimal form does not terminate and is shown here to 10 significant figures (more with the precision selector).
Sources
- Guide for the Use of the International System of Units (SI), NIST Special Publication 811, 2008 Edition, National Institute of Standards and Technology .
- Guide for the Use of the International System of Units (SI), NIST Special Publication 811, 2008 Edition, National Institute of Standards and Technology , Appendix B.8, "mil".
Last reviewed: . Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.
Cite this page
APA
Scientific Converters. (2026, October 15). Convert Micrometres per Year to Mils per Year (µm/y to mpy). Retrieved October 25, 2026, from https://scientificconverters.com/corrosion-rate/micrometers-per-year-to-mils-per-year/
IEEE
Scientific Converters, "Convert Micrometres per Year to Mils per Year (µm/y to mpy)," scientificconverters.com. Accessed: Oct. 25, 2026. [Online]. Available: https://scientificconverters.com/corrosion-rate/micrometers-per-year-to-mils-per-year/