Activation Energy Calculator

Enter two (k, T) data points and get the activation energy Ea using the two-point Arrhenius equation.

Use the Activation Energy Calculator

Two Data Points

Ea = −R · ln(k₂/k₁) / (1/T₂ − 1/T₁)

Data Point 1

Data Point 2

Enter two (k, T) pairs and click Calculate Ea.

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Summary

The Activation Energy Calculator uses the two-point form of the Arrhenius equation, ln(k2/k1) = −(Ea/R) × (1/T2 − 1/T1), to determine activation energy Ea from two experimental rate-constant measurements at different temperatures. No pre-exponential factor A is needed — only k1 at T1 and k2 at T2. The tool also back-calculates A so you have the complete Arrhenius parameters for the reaction. All computation runs in your browser with no data sent to any server.

How it works

  1. Enter the rate constant k1 (any positive number) measured at temperature T1.
  2. Enter the rate constant k2 measured at a different temperature T2.
  3. Choose Kelvin or Celsius for the temperature inputs.
  4. Click Calculate — the tool applies ln(k2/k1) = −(Ea/R)(1/T2 − 1/T1) to solve for Ea.
  5. Review the result in both J/mol and kJ/mol, the back-calculated pre-exponential factor A, and the step-by-step substitution.
  6. Click Reset to clear all fields and start a new calculation.

Use cases

  • Extract activation energy from two rate constant measurements in a kinetics experiment.
  • Determine Ea without needing to know the pre-exponential factor A.
  • Verify activation energies calculated by hand before submitting lab reports.
  • Compare Ea values for catalyzed vs. uncatalyzed reactions.
  • Prepare for AP Chemistry, MCAT, or physical chemistry exams involving Arrhenius kinetics.
  • Estimate how much faster a reaction will run at a higher temperature given experimental k data.
  • Model food spoilage or shelf-life degradation using rate constant ratios.
  • Screen reaction candidates by comparing Ea values across data points.

Frequently Asked Questions

Last updated: 2026-09-30 · Reviewed by Nham Vu