Convert Mils per Year to Micrometres per Year (mpy to µm/y)

Formula

µm/y = mpy × 25.4

Derivation from SI units:

• 1 mpy = 0.001 in per year = 0.0254 mm/y (exact)
• 1 µm/y = 0.001 mm/y
• 1 mpy = 0.0254 mm/y ÷ 0.001 mm/y per µm/y = 25.4 µm/y

Both units are defined exactly, so the factor is exact. Mil per Year definition: mil per year; Micrometre per Year definition: micrometre per year.

Worked examples

1. A rate of 2 mpy is 50.8 µm/y.
   2 mpy × 25.4 = 50.8 µm/y
2. A rate of 0.5 mpy is 12.7 µm/y.
   0.5 mpy × 25.4 = 12.7 µm/y

Where it's used

Corrosion rates in mpy are converted to µm/y for ISO corrosivity categories and low-rate atmospheric exposure. Multiply by 25.4.

Mil per Year to other corrosion rate units

Frequently asked questions

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".
• Guide for the Use of the International System of Units (SI), NIST Special Publication 811, 2008 Edition, National Institute of Standards and Technology .

Last reviewed: 2026-10-15. Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.