First Order Kinetics Calculator
Enter any three values in one consistent time and concentration system. The fourth value and half-life are calculated locally.
A QUICK WALKTHROUGH
How to use this tool
- Enter any three of [A]0, [A]t, t, and k.
- Use consistent time units and nonnegative concentrations.
- Calculate the missing value and review the half-life.
Constant first-order model
The calculator uses ln([A]t/[A]0) = −kt and t1/2 = ln(2)/k. It does not determine reaction order or fit experimental data.
Units and limits
Concentrations must be positive when used in a logarithm, k must be positive, and t must be nonnegative. Use one consistent time unit for t, k, and half-life.
GOOD TO KNOW
Common questions
Does this determine reaction order?
No. It applies the constant first-order model you selected.
What values can be solved?
Any three of initial concentration, final concentration, elapsed time, and rate constant solve the fourth; half-life is also shown.
Are values uploaded?
No. Calculation happens in this browser.