About this tool
The Arrhenius Equation Calculator is a free, in-browser chemical-kinetics tool built on k = A · exp(−Ea ⁄ (R·T)), which describes how a reaction's rate constant depends on temperature. In single-point mode you enter three of the four quantities — rate constant k, pre-exponential factor A, activation energy Ea, and temperature T — and it solves for the fourth. In two-point mode you supply two rate constants at two temperatures and it returns the activation energy.
Activation energy can be entered and displayed in kJ/mol or J/mol; internally it is always converted to J/mol to match the gas constant R = 8.314 J/mol·K. Single-point rearrangements are k = A·exp(−Ea ⁄ (R·T)), A = k·exp(Ea ⁄ (R·T)), Ea = −R·T·ln(k ⁄ A), and T = −Ea ⁄ (R·ln(k ⁄ A)). The two-point method uses ln(k₂ ⁄ k₁) = −(Ea ⁄ R)(1 ⁄ T₂ − 1 ⁄ T₁), which rearranges to Ea = R·ln(k₂ ⁄ k₁) ⁄ (1 ⁄ T₁ − 1 ⁄ T₂); the pre-exponential factor is then recovered from A = k₁·exp(Ea ⁄ (R·T₁)).
Everything runs locally in your browser with nothing uploaded. Temperatures must be in kelvin and above absolute zero, and k and A must be positive when a logarithm of their ratio is taken. A and k share the same units, which depend on the reaction order, so they are reported as plain numbers.