Arrhenius Equation Solver
Use k = A · e-Ea/(R·T). Enter any three values and leave exactly one field blank to solve for it.
Two-Temperature Arrhenius Calculator
Use this form to calculate activation energy from two measured rates, or predict a new rate at another temperature.
What is the Arrhenius equation?
The Arrhenius equation connects reaction speed and temperature. In plain terms, it helps explain why chemical reactions usually happen faster when things get hotter. It is one of the most useful equations in kinetics, chemical engineering, materials science, food science, and pharmaceutical stability studies.
The classic form is: k = A · e-Ea/(R·T), where k is the rate constant, A is the frequency factor, Ea is activation energy, R is the gas constant, and T is absolute temperature in Kelvin.
How to use this Arrhenius equation calculator
Single-point solver
In the first calculator, type values for any three variables and leave one blank. The tool solves for the missing variable directly from the Arrhenius expression.
- Leave k blank to calculate the rate constant at a given temperature.
- Leave A blank to find the pre-exponential factor.
- Leave Ea blank to estimate activation energy from known k, A, and T.
- Leave T blank to estimate the temperature needed to achieve a desired k.
Two-temperature solver
In the second calculator, switch between two practical modes:
- Find Ea: use two measured rate constants at two temperatures.
- Find k₂: predict a new rate constant when temperature changes.
Important unit notes
Temperature must always be entered in Kelvin. If you have Celsius, convert with: K = °C + 273.15. Activation energy can be entered in either J/mol or kJ/mol using the unit selector.
The gas constant used in this page is R = 8.314462618 J·mol⁻¹·K⁻¹.
Worked example
Suppose a reaction has A = 1.2 × 107, Ea = 65 kJ/mol, and T = 310 K. Leave k blank in the first calculator and click Calculate. The result is the predicted rate constant at that temperature.
If you then want to know how much the rate changes at a new temperature, use the second calculator in “Find k₂” mode with your original k₁, T₁, and target T₂.
Common mistakes to avoid
- Using Celsius instead of Kelvin.
- Mixing J/mol and kJ/mol without converting.
- Entering zero or negative values for k, A, or temperature.
- Leaving more than one field blank in the single-point solver.
Why Arrhenius calculations matter
Arrhenius modeling is essential for shelf-life prediction, catalyst design, battery degradation studies, corrosion analysis, and process optimization. Even a simple calculator can speed up lab decisions and help verify spreadsheet or simulation results quickly.