Arrhenius Equation Calculator
One tool for the Arrhenius relationship. Choose whether to calculate a rate constant from the pre-exponential factor and activation energy, to find the activation energy from rate constants at two temperatures, or to predict the rate constant at a second temperature. Temperatures are converted to kelvin internally.
Last updated: September 26, 2026
Frequently asked questions
How is this different from an Activation Energy Calculator?
It includes one. Choose the second mode to find the activation energy from two rate constants and two temperatures. Both use the same Arrhenius relationship, so they are in one tool rather than two pages that rearrange the same equation.
What does the Arrhenius equation say?
The rate constant grows exponentially with temperature: k = A·exp(−Ea/RT). A larger activation energy makes the reaction more sensitive to temperature.
Why does the calculator use kelvin?
The equation involves 1/T and an absolute temperature scale, so Celsius or Fahrenheit inputs are converted to kelvin first. Using °C directly gives wrong results.
What units do A and k have?
They share units that depend on the reaction order, for example s⁻¹ for first order. The exponent −Ea/RT is dimensionless.
How accurate is the two-point activation energy?
It assumes a constant activation energy and Arrhenius behavior between the two temperatures. Using more than two temperatures, in an Arrhenius plot, is more reliable in practice.
Do all reactions follow the Arrhenius equation?
No. Many do over limited ranges, but some do not, especially those with complex mechanisms, enzyme denaturation, or wide temperature spans.