When to use this calculator
Find half-life from a first-order reaction rate constant. This concentration-independent half-life is specific to a first-order model.
Explore the reaction quantities & yield calculators for other questions in this topic. For a related calculation, use the First Order Reaction Remaining Calculator: Estimate reactant concentration after a first-order reaction interval.
PUTTING IT INTO PRACTICE
First Order Reaction Half Life: a worked example
The values below are an illustrative example, not a recommendation. Replace them with measurements or assumptions that match your question.
| Input | Example value |
|---|---|
| Rate constant (1/s) | 0.1 |
| Result | 6.931472 s |
- Check the input labels and enter the example values above.
- Apply the relationship: Half-life = ln(2)/rate constant.
- The result is 6.931472 s, rounded for display.
How to interpret your result
This concentration-independent half-life is specific to a first-order model.
Balance the chemical equation before using mole ratios. Identify the limiting reactant separately. Yield, purity and atom economy measure different aspects of a reaction and should not be substituted for one another.
Frequently asked questions
Is percent yield the same as atom economy?
No. Yield compares actual product against a theoretical amount; atom economy describes stoichiometric use of reactant mass in the desired product.
When is the first order reaction half life calculator useful?
Find half-life from a first-order reaction rate constant. This concentration-independent half-life is specific to a first-order model.
How do I use the first order reaction half life calculator?
Enter rate constant (1/s). The result updates automatically. Use the units shown beside each input; the example values illustrate the method.
Which formula does this calculator use?
Half-life = ln(2)/rate constant.
What should I check before using the result?
This concentration-independent half-life is specific to a first-order model.
How are results rounded?
Scalar numbers display up to six decimal places, with scientific notation for very large or small values. Text, fraction, date and schedule outputs use the format described on the tool. Intermediate calculations use JavaScript floating-point arithmetic. Keep sensible precision for your measurements.
Further reading
For background on this topic, see OpenStax: quantitative chemical analysis ↗. This is a topic reference, not an external review or endorsement of this tool.
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