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Kinetics · Rate laws

Reaction Rate Law & Integrated Kinetics Calculator

Calculate reaction rate or a rate constant from a two-reactant rate law, and solve zero-, first-, or second-order integrated kinetics problems.

Formula shown Runs locally Reviewed Aug 11, 2026
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Equation guide

Empirical rate laws at constant temperature and integrated single-reactant models

Differential rate law

r = k[A]m[B]norder = m + n

Zero and first order

[A]t = [A]0 − ktln[A]t = ln[A]0 − kt

Second order

1/[A]t = 1/[A]0 + kt
Reaction kinetics

Model rate or concentration over time

r = k[A]m[B]n

Reaction orders may be zero or positive and are experimental. Use one consistent time unit. Inputs and displayed results use at most three decimal places.

r = k[A]ᵐ[B]ⁿ

Enter a consistent experimental rate law or integrated kinetic state.

Using the model

Symbols, assumptions and limitations

Interpretation notes

Reaction orders are empirical and are not generally equal to balanced-equation coefficients. Concentrations must be in mol/L and time must use one consistent unit. Integrated forms assume a single reactant, constant temperature, constant volume, and one unchanging rate law.

Worked examples

See the method in practice

01

Two-reactant rate law

For r = k[A]²[B], doubling A multiplies rate by four, while doubling B multiplies it by two; the overall order is three.

02

First-order decay

For a first-order process, [A]t = [A]0e⁻ᵏᵗ and the half-life is ln 2/k, independent of initial concentration.

Questions

Frequently asked

Can reaction order be read from the balanced equation?

Usually not. Orders must be determined experimentally, except for an established elementary step.

Why do the units of k change?

The rate always has concentration-per-time units, so the dimensions of k compensate for the overall reaction order.

Does a catalyst change the equilibrium constant?

No. A catalyst changes forward and reverse rates, helping equilibrium to be reached faster without changing its position.

Sources & review

Equations and examples are checked against the references below. Results are educational and should be independently verified for safety-critical work.

OpenStax Chemistry — Factors Affecting Reaction Rates OpenStax Chemistry — Integrated Rate Laws

Written by the STEM Hub editorial team · Reviewed August 11, 2026 · Review methodology