Use this chemistry calculator to reproduce a named relationship with explicit quantities and units for study, laboratory planning, or an independent numerical check.

Rate constant k (1/s)

Required number input.

Compute the half-life of a first order reaction as the natural logarithm of two divided by the rate constant. The tool evaluates the supplied inputs together and returns the named outputs below; it does not infer omitted operating conditions or change the units shown.^[1]

Half-life (s)

The resulting half-life returned as a number.

• Radioactive and nuclear calculations require the correct isotope, decay mode, mass convention, and time unit. Branching, daughter products, detector efficiency, shielding, and uncertainty in tabulated nuclear data may require a fuller model.
• Use finite inputs in the displayed units and preserve more precision than the final presentation requires. Independently verify safety-critical, financial, compliance, or production decisions.

Check units and significant figures, compare the result with limiting cases, and use measured or source-specific constants where available. Laboratory, safety, and regulatory decisions require validated methods and appropriate uncertainty analysis.

• Second Order Half-Life Calculator

  Compute the second-order half-life t½ = 1/(k·[A]₀) from a rate constant and initial concentration.

• Zero Order Half-Life Calculator

  Compute the zero-order half-life t½ = [A]₀/(2k) from a rate constant and initial concentration.

• Pseudo First Order Rate

  Compute the observed pseudo first order rate constant for a second order reaction with one reactant in large excess.