ONE FORMULA, ONE ANSWER
First Order Half Life Calculator
Check the half life of an ideal first-order disappearance or decay process. Choose input units and calculate one value within the stated conditions.
Inputs
Calculations run in this browser. Scientific notation such as 1.2e-3 is supported. Do not group thousands.
Result
First-order half life t_½
Enter values and select Calculate.
t_1/2 = ln(2) / k
Assumptions
Use k>0 and a first-order disappearance or decay model with constant k. Do not apply this result to zero-order or second-order reactions, medication dosing or treatment decisions.
Displayed values are floating-point approximations. Measurement uncertainty and design safety factors are not calculated.
Formula references and credits
NaNa Lab created the code, descriptions, icons and preview images. Text, figures and code from the linked references have not been reproduced.
Physical constants: NIST / CODATA 2022. The values of μ₀ and ε₀ are measured recommendations, not exact defining constants. Values and precision notes are in the source record.
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