Arrhenius Equation Calculator – Free, with Steps

Arrhenius equation calculator: rate constant, activation energy, pre-exponential factor or temperature from k = A·e^(−Ea/RT).

How to use this calculator

Choose the quantity you want under “Solve for”.
Type the known values and pick their units: any combination works.
The result updates as you type. Open “Show the steps” to see the substitution.

The Arrhenius equation k = A·e^−Ea/(RT) describes how a rate constant k grows with temperature. E_a is the activation energy and A the pre-exponential (frequency) factor.

A common rule of thumb is that many reactions near room temperature double their rate for every 10 °C, which corresponds to E_a of about 50 kJ/mol.

Formula

k = A · e^{−E_a/(R·T)}

Symbol	Quantity	Units
A	Pre-exponential factor	s⁻¹, min⁻¹, h⁻¹
E_a	Activation energy	kJ/mol, J/mol, kcal/mol, cal/mol
T	Temperature	K, °C, °F, °R
k	Rate constant	s⁻¹, min⁻¹, h⁻¹

Constants used: R = 8.314462618 J·mol⁻¹·K⁻¹

Worked example

Given: A = 1 × 10¹³ s⁻¹ · E_a = 100 kJ/mol · T = 25 °C

k = A · e^−Ea/(R·T)

Result: k = 3.02523 × 10^-5 s⁻¹

Rate constant for different values of Pre-exponential factor

A · Pre-exponential factor	k · Rate constant
5 × 10¹² s⁻¹	1.5126 × 10^-5 s⁻¹
7.5 × 10¹² s⁻¹	2.2689 × 10^-5 s⁻¹
9 × 10¹² s⁻¹	2.7227 × 10^-5 s⁻¹
1 × 10¹³ s⁻¹	3.0252 × 10^-5 s⁻¹
1.1 × 10¹³ s⁻¹	3.3277 × 10^-5 s⁻¹
1.25 × 10¹³ s⁻¹	3.7815 × 10^-5 s⁻¹
1.5 × 10¹³ s⁻¹	4.5378 × 10^-5 s⁻¹
2 × 10¹³ s⁻¹	6.0505 × 10^-5 s⁻¹

Other values as in the worked example.

Frequently asked questions

How do I find Ea from two temperatures?

Use ln(k₂/k₁) = −(Ea/R)·(1/T₂ − 1/T₁). Equivalently, compute A at one temperature with this calculator and solve for Ea with the other point.

What units does A have?

The same as k. For a first-order reaction that is s⁻¹.

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Last updated: November 7, 2026 · Report an error