Larson-Miller Parameter Calculator

Inputs

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Metal temperature during the exposure. Converted to Kelvin internally.
°C
Time at temperature, in hours.
h
The Larson-Miller constant fitted to the material rupture data; 20 is the classic default for steels.
Second temperature for the constant-LMP time trade (e.g. an accelerated test or a hotter service point).
°C

Results

Default result
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Larson-Miller parameter(LMP)
19.76
Pass

Enter this into the material's LMP master curve to read the rupture or creep stress.

T_K·(C + log10 t)/1000 — the kilo-convention used in most LMP master curves.

Also computed

Equivalent time at T₂(t₂)1,961h

The hotter what-if point reaches the same creep damage 5.1× faster — the acceleration factor of a furnace test at T₂.

Time at the what-if temperature producing the same LMP.

Time ratio(t₂/t₁)0.196

T₁ absolute(T₁)823.15K

T₂ absolute(T₂)848.15K

Method notes 3 notes
  • LMP collapses time-temperature creep data onto one master curve per material. The parameter itself is exact arithmetic; ALL design meaning comes from the material's fitted master curve and constant C.
  • The kilo-divided convention (÷1000) matches most published steel master curves (typical steels: LMP ≈ 15-25 with C = 20). Some references omit the ÷1000 or use Rankine — check the curve's convention before comparing.
  • Constant-LMP trading assumes the same damage mechanism at both temperatures; large extrapolations across microstructural changes (carbide coarsening, phase changes) are unreliable.

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