Reaction kinetics & half-life calculator

Q: How should I format data for the fitting and Arrhenius modes?

For data fitting, paste time and concentration pairs as t, A on separate lines (all A values must be positive). For Arrhenius plots, paste T, k pairs with T in kelvins and k > 0. The calculator performs straight-line fits to the transformed data and reports slopes, intercepts, R² and kinetic parameters.

How to use (3 steps)

Choose a mode: integrated rate law, data fitting, or Arrhenius.
Enter A₀, k and t for theory, paste measured (t, [A]) or (T, k) data for fitting.
Read off [A](t), fraction remaining, t₁/₂, best-fit order and Arrhenius parameters, then copy the URL to share the setup.

A default 1st-order example and small datasets are preloaded so you can compare realistic values before you compute.

Inputs

Pick a mode, adjust the example numbers or paste your own data. Be sure that the units of k and t (or T and k) are consistent within a given calculation.

Integrated rate law Data fitting (0th/1st/2nd) Arrhenius (ln k vs 1/T)

Reaction order n

Initial concentration [A]₀ (mol/L)

Rate constant k (units depend on order)

For 0th order k has units of mol·L⁻¹·time⁻¹, for 1st order time⁻¹, and for 2nd order L·mol⁻¹·time⁻¹.

Time t (consistent with k)

Results

Mode: Integrated rate law

This section summarizes the main quantities computed from your inputs (concentration, fraction remaining, half-life, fitted constants and Arrhenius parameters).

How it's calculated

Choose a mode and compute to show the transformed plots, fit diagnostics, and calculation steps.

Using the kinetics, fitting, and Arrhenius modes

This page supports three related tasks: direct rate-law calculations, fitting concentration-time data, and Arrhenius analysis. Start by picking the mode that matches the data you actually have.

Suggested workflow

Use the calculator mode when you already know the order and rate constant and want concentration, time, or half-life.
Use data fitting when you have a concentration-time table and want to compare 0th, 1st, and 2nd-order linearisations.
Use the Arrhenius mode when you have temperature-rate pairs and need activation energy from a straight-line fit of ln k vs 1/T.

What the fitting mode assumes

The fitting workflow is built for a single reactant that decays with time. If your pasted series rises instead of decays, the calculator now flags that mismatch instead of pretending it found a valid decay model.

Common mistakes to avoid

Pasting comma-decimal data with comma separators in locales that expect semicolons for ambiguous rows.
Comparing R² values without first checking whether the chosen model is chemically plausible.
Using the half-life relation from one reaction order in a mode that was fitted as another order.

FAQ

Which reaction orders does this tool support?

It focuses on simple 0th, 1st and 2nd order kinetics for a single reactant A, using the integrated forms [A](t) = [A]₀ − k t, ln[A] = ln[A]₀ − k t and 1/[A] = 1/[A]₀ + k t. For more complex mechanisms or mixed orders, treat this calculator as a first diagnostic rather than a full kinetic model.

How should I format data for the fitting and Arrhenius modes?

For data fitting, paste time and concentration pairs as t, A on separate lines (all A values must be positive). For Arrhenius plots, paste T, k pairs with T in kelvins and k > 0. The calculator performs straight-line fits to the transformed data and reports slopes, intercepts, R² and kinetic parameters.

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