Activation Energy Calculator

How to Use This Calculator

1. Enter k₁ at T₁ and k₂ at T₂ (same units).
2. The calculator returns Ea in kJ/mol and J/mol.
3. Use the Find k at New Temp tab to extrapolate the rate constant to any temperature.

Formula

Example

Frequently Asked Questions

• What is activation energy? ▼
  Activation energy (Ea) is the minimum energy required for reactant molecules to successfully collide and form products. Higher Ea means a slower reaction at a given temperature.
• What is the Arrhenius equation? ▼
  k = A·exp(−Ea/(RT)), where k is the rate constant, A is the pre-exponential factor, Ea is activation energy in J/mol, R = 8.314 J/(mol·K), and T is temperature in Kelvin.
• How do I calculate Ea from two rate constants? ▼
  Ea = R × ln(k₂/k₁) × (T₁T₂)/(T₂−T₁). This two-point Arrhenius method assumes Ea and A are constant over the temperature range.
• What is the Arrhenius plot? ▼
  A plot of ln(k) vs 1/T gives a straight line with slope = −Ea/R. The activation energy is found from: Ea = −slope × R.
• What are typical activation energies? ▼
  Most chemical reactions have Ea = 40–150 kJ/mol. Enzyme-catalyzed reactions typically 25–65 kJ/mol. Uncatalyzed biological reactions: 65–110 kJ/mol. A catalyst lowers Ea without changing ΔH.

Related Calculators