Arrhenius Equation Calculator
Calculate a rate constant from activation energy and temperature, or predict its change between two temperatures.
01 Set up your calculation
- Choose a frequency factor or a known reference rate.
- Enter molar activation energy and the target temperature.
- Keep both rate quantities in the same units, then inspect the predicted rate constant.
02 The relationship
For the assumptions behind these results, read the explanation below. You can also explore Activation Energy and Michaelis–Menten Equation.
Follow the numbers
With A = 10¹⁰ s⁻¹, Eₐ = 50 kJ/mol, and T = 350 K, k is approximately 345.187 s⁻¹.
03 Temperature changes the exponential term
The Arrhenius equation combines a frequency factor with a temperature-dependent exponential. The frequency factor sets the rate scale, while the activation energy controls how sensitively that rate responds to temperature. This tool keeps the numerical rate units chosen for the supplied factor or reference rate.
For a positive activation energy, increasing temperature increases the calculated rate. A fixed increase of ten degrees does not give a universal rate multiplier; the starting temperature and activation energy both matter.
04 When extrapolation becomes unreliable
A fitted Arrhenius relationship is most useful over the temperature interval where the mechanism, phase, and other conditions remain comparable. Phase changes, catalyst changes, denaturation, and transport limitations can invalidate a straightforward extrapolation.
The calculation uses energy per mole and the molar gas constant. A per-molecule energy would require Boltzmann’s constant instead. Do not enter a per-particle number into the molar energy field.
Questions from the notebook
Is rate constant the same as reaction rate?
No. The rate law also includes concentrations and their powers.
Why does the output say the same units?
Rate-constant units depend on reaction order, so the tool preserves the units of your input rather than assuming first-order kinetics.
Can a negative activation energy be entered?
Yes, for a measured apparent Arrhenius parameter. Interpret it in the context of the mechanism and data.
References & reading
- OpenStax, Rice University — Collision Theory ↗
Explains the Arrhenius equation, its logarithmic form, activation energy, and temperature dependence.
- NIST — Guide to SI conversion factors ↗
Supports physical unit conversions. Input values are converted to the formula’s base units before calculation.
Our explanations are written for ChemistryCalc. Read how we build and check our tools. These calculations are educational estimates where the underlying model requires assumptions.