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Chemistry

Arrhenius Equation Calculator

k = A exp(-Ea / RT). Free online Arrhenius Equation Calculator. Calculate arrhenius equation online — fast, accurate, mobile-friendly, no signup needed.

k
0.000713

Derivation

  1. ├── 01GivenA = 10000000000, Ea = 75000, T = 298
  2. ├── 02Formulat × exp(-a / (8.314 × n))
  3. └── 03Compute k7.1322e-4
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§01What is

Understanding the Arrhenius Equation Calculator

The Arrhenius Equation Calculator computes k from 3 inputs: a (pre-exp), ea (j/mol), t (k). k = A exp(-Ea / RT).

Chemistry turns grams and moles into reactions. Getting the stoichiometry, dilutions, or concentrations right is the difference between a lab result you can trust and one you can’t reproduce. The Arrhenius Equation Calculator sits in that toolkit — it k = A exp(-Ea / RT). Enter your numbers above and the result updates instantly; every step of the math is shown in the Derivation panel so you can see exactly how the answer was reached.

§02The Formula

How it’s calculated

t × exp(-a / (8.314 × n))

Where

A
A (pre-exp)
Ea
Ea (J/mol)
T
T (K)
§03Practical Example

Step-by-step walkthrough

Scenario

Apply the formula to a realistic set of inputs: A (pre-exp) = 10000000000, Ea (J/mol) = 75000, T (K) = 298.

  1. 01Start by noting the input — A (pre-exp): 10000000000.
  2. 02Start by noting the input — Ea (J/mol): 75000.
  3. 03Start by noting the input — T (K): 298.
  4. 04Substitute these values into the formula: t × exp(-a / (8.314 × n))
  5. 05Compute k: the calculator returns 0.000713219.
  6. 06Cross-check the answer by opening the Derivation panel above — every line of math is shown so you can follow the computation end-to-end.
§04Variants

Common Arrhenius Equation Problems

The formula gets rearranged depending on which variable you need. Here are the patterns you’ll run into in the real world — find the one that matches your problem and follow the worked steps.

01 · PATTERN

A (pre-exp) halved

A = 5.00000e+9 (from 1.00000e+10)

Keep every other input at its default and halve the a (pre-exp). See how k responds.

  1. 01New A (pre-exp): 5.00000e+9
  2. 02Baseline k: 0.000713219
  3. 03New k: 0.00035661
  4. 04k decreases by 50% → use this sensitivity to plan for real-world variation.
02 · PATTERN

A (pre-exp) doubled

A = 2.00000e+10 (from 1.00000e+10)

Keep every other input at its default and double the a (pre-exp). See how k responds.

  1. 01New A (pre-exp): 2.00000e+10
  2. 02Baseline k: 0.000713219
  3. 03New k: 0.00142644
  4. 04k increases by 100% → use this sensitivity to plan for real-world variation.
03 · PATTERN

Ea (J/mol) halved

Ea = 37500 (from 75000)

Keep every other input at its default and halve the ea (j/mol). See how k responds.

  1. 01New Ea (J/mol): 37500
  2. 02Baseline k: 0.000713219
  3. 03New k: 2670.62
  4. 04k increases by 374445223.2% → use this sensitivity to plan for real-world variation.
04 · PATTERN

Ea (J/mol) doubled

Ea = 150000 (from 75000)

Keep every other input at its default and double the ea (j/mol). See how k responds.

  1. 01New Ea (J/mol): 150000
  2. 02Baseline k: 0.000713219
  3. 03New k: 5.08682e-17
  4. 04k decreases by 100% → use this sensitivity to plan for real-world variation.
§05FAQ

Frequently asked questions

Yes. The calculator implements the standard formula as documented and returns exact floating-point results. No approximations are used unless noted in the formula.
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