Activation Energy Calculator

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Determine the activation energy (Ea) for a reaction using the Arrhenius equation.

Reaction Parameters

Rate Constant (k)

Pre-exponential Factor (A)

Temperature (K)

Calculation Results

Enter the reaction parameters to calculate activation energy

About this calculator

Overview

Activation energy (Eₐ) is the minimum energy barrier that reactant molecules must overcome to transform into products. Think of it as a hill that molecules need to climb before they can roll down into the lower-energy valley of products. This concept explains why reactions don't happen instantly and why temperature and catalysts affect reaction rates.

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Pro Tips

Temperature must be in Kelvin (K = °C + 273.15)—room temperature is 298 K, not 25 K!
Rate constant (k) units depend on reaction order: s⁻¹ for first-order, M⁻¹s⁻¹ for second-order, etc.
Pre-exponential factor (A) has the same units as k and represents maximum possible reaction rate.
For accurate results, use rate constants measured at the same temperature you're inputting.
Activation energies are usually positive—negative values suggest calculation errors.

Arrhenius Equation Details

The Arrhenius equation k = A * e^(-Ea/RT) links temperature and activation energy to the rate constant. As temperature (T) increases, the exponential term becomes less negative, causing 'k' to increase rapidly.