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Rate Constant from First-Order Half-Life Calculator

k = ln(2) / t½ — first-order rate constant from half-life.

Calculates the first-order rate constant k from the half-life t½ and reports the corresponding rate constant in inverse time units.

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Dr. Helena Ortiz By Dr. Helena Ortiz
Published Last reviewed 1 min read

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How to use this calculator

  1. Fill in the inputs above using the units you already have.
  2. Values update automatically as you type — no submit button needed.
  3. Hover any result row for the underlying formula and intermediate values.

Formula

k = ln(2) / t½; t½ = ln(2) / k

In depth

Calculates the first-order rate constant k from the half-life t½ and reports the corresponding rate constant in inverse time units.