Convert Millimetres per Year to Mils per Year (mm/y to mpy)
1 millimetre per year (mm/y) = 39.37007874 mils per year (mpy). 1 mpy = 0.0254 mm/y. Example: 0.1 mm/y = 0.1 × 39.37007874 = 3.937007874 mpy.
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1 mm/y = 39.37007874 mpy
Type in either box. Scientific notation works: 1.5e-3.
Converting a list? Use the bulk millimetre per year to mil per year converter to paste a column from Excel.
How to Convert Millimetre per Year to Mil per Year
- 1 mm/y = 39.37007874 mpy
- 1 mpy = 0.0254 mm/y
- Example: convert 0.1 mm/y to mpy: 0.1 mm/y = 0.1 × 39.37007874 mpy = 3.937007874 mpy
Formula
mpy = mm/y × 39.37007874016
Derivation from SI units:
- Thickness loss in millimetres per year of exposure (the reference unit for corrosion rate)
- 1 mpy = 0.001 in per year = 0.0254 mm/y (exact)
Both units are defined exactly, so the factor is exact. Millimetre per Year definition: millimetre per year; Mil per Year definition: mil per year.
Worked examples
- A corrosion rate of 0.1 mm/y is 3.937007874 mpy.
0.1 mm/y × 39.37007874 = 3.937007874 mpy - A 0.5 mm/y rate is 19.68503937 mpy.
0.5 mm/y × 39.37007874 = 19.68503937 mpy
Millimetre per Year to Mil per Year conversion table
| Millimetres per Year (mm/y) | Mils per Year (mpy) |
|---|---|
| 0.001 mm/y | 0.03937007874 mpy |
| 0.01 mm/y | 0.3937007874 mpy |
| 0.025 mm/y | 0.9842519685 mpy |
| 0.05 mm/y | 1.968503937 mpy |
| 0.1 mm/y | 3.937007874 mpy |
| 0.13 mm/y | 5.118110236 mpy |
| 0.25 mm/y | 9.842519685 mpy |
| 0.5 mm/y | 19.68503937 mpy |
| 1 mm/y | 39.37007874 mpy |
| 1.27 mm/y | 50 mpy |
| 5 mm/y | 196.8503937 mpy |
Where it's used
Corrosion rates in mm/y are converted to mpy for US oil, gas and process-industry reports. Multiply by about 39.37.
Millimetre per Year to other corrosion rate units
| Conversion | 1 mm/y equals |
|---|---|
| millimetre per year to mil per year | 39.37007874 mpy |
| millimetre per year to micrometre per year | 1000 µm/y |
| millimetre per year to inch per year | 0.03937007874 ipy |
Frequently asked questions
How many mpy is 1 mm/y?
1 mm/y = 39.3701 mpy.
How many mils per year are in 1 millimetre per year?
1 mm/y = 39.37007874 mpy.
How do I convert millimetres per year to mils per year?
Multiply the value in mm/y by 39.37007874. For example, 0.1 mm/y × 39.37007874 = 3.937007874 mpy.
Is the mm/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 Millimetres per Year to Mils per Year (mm/y to mpy). Retrieved October 25, 2026, from https://scientificconverters.com/corrosion-rate/millimeters-per-year-to-mils-per-year/
IEEE
Scientific Converters, "Convert Millimetres per Year to Mils per Year (mm/y to mpy)," scientificconverters.com. Accessed: Oct. 25, 2026. [Online]. Available: https://scientificconverters.com/corrosion-rate/millimeters-per-year-to-mils-per-year/