Mil per Year (mpy)
The mil per year (mpy) is the US unit of corrosion rate: one thousandth of an inch of thickness lost per year, exactly 0.0254 mm/y. Below about 1 mpy corrosion is usually considered low.
Symbol: mpy
Quantity: corrosion rate (thickness loss per year)
SI relation: 1 mpy = 0.0254 mm/y (exact)
Derivation: 1 mpy = 0.001 in per year = 0.0254 mm/y (exact)
Exact: yes, by definition
Typical uses
- US oil, gas and process industry corrosion monitoring
- Corrosion coupon reports
- Material compatibility tables
Convert mils per year to other units
| Conversion | 1 mpy equals | Reverse |
|---|---|---|
| mil per year to millimetre per year | 0.0254 mm/y | millimetre per year to mil per year |
| mil per year to micrometre per year | 25.4 µm/y | micrometre per year to mil per year |
| mil per year to inch per year | 0.001 ipy | inch per year to mil per year |
Open the Corrosion Rate Converter to convert any value between all units.
Sources
- 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). Mil per Year (mpy). Retrieved October 25, 2026, from https://scientificconverters.com/units/mil-per-year/
IEEE
Scientific Converters, "Mil per Year (mpy)," scientificconverters.com. Accessed: Oct. 25, 2026. [Online]. Available: https://scientificconverters.com/units/mil-per-year/