How it works
Remaining amount = initial amount × 2^(−elapsed time / half-life).
Input definitions
- Initial amount
- Enter the value in the labeled unit.
- Half-life (time units)
- Enter the value in the labeled unit.
- Elapsed time in the same units
- Enter the value in the labeled unit.
A worked example
- Initial amount
- 100
- Half-life (time units)
- 10
- Elapsed time in the same units
- 20
Assumptions & limits
Uses the units and scope stated in the input labels. Results are rounded for display; verify the model is appropriate for your situation.
Sources & review
Maintained by AnsRio. Methods and examples use automated checks; this does not imply independent professional certification.
Method updated 2026-10-18. Content checked against the stated method and examples. Our verification approach.
Common questions
Must elapsed time and half-life use the same units?
Yes. Use seconds for both, years for both, or another consistent time unit. The decay rate is assumed constant.
How does Exponential decay and remaining amount work?
Remaining amount = initial amount × 2^(−elapsed time / half-life).
What should I check before using Exponential decay and remaining amount?
Uses the units and scope stated in the input labels. Results are rounded for display; verify the model is appropriate for your situation.