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 (L/(mol·s))

Rate constant k in L·mol⁻¹·s⁻¹; must be greater than zero.

Initial concentration (mol/L)

Initial reactant concentration [A]₀ in mol/L.

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

Half-life in seconds.

• 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.

• Zero Order Half-Life Calculator

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

• First Order Half-Life

  Compute the half-life of a first order reaction as the natural logarithm of two divided by the rate constant.

• Pseudo First Order Rate

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