Formula
remaining=initial ×2^(−elapsed/half-life).
- Use the units shown beside each field.
- Results update automatically whenever you change an input.
- Displayed values use up to four decimal places, or scientific notation for very small or large numbers. Calculations use standard floating-point arithmetic; exact integer and fraction tools identify their own precision rules.
- Single isolated exponential-decay species; daughter production and exposure/dose are not modeled.
Example Calculation
Example inputs
- Initial amount: 100
- Elapsed time: 20 time units
- Half-life: 10 same time units
Initial amount = 100; Elapsed time = 20; Half-life = 10. Primary result: 25.
Frequently asked questions
How do I use this calculator?
Enter initial amount, elapsed time, half-life. The result updates automatically. Use Reset to restore the example values.
What method does it use?
remaining=initial ×2^(−elapsed/half-life).. Single isolated exponential-decay species; daughter production and exposure/dose are not modeled.
Why might a rounded result differ?
The calculation keeps full numeric precision internally, then rounds the displayed result. Rounding intermediate steps by hand can produce a slightly different answer.
Are my inputs saved online?
No. This calculator processes your inputs in your browser. A recently used list stores only calculator names on this device, not your entered values.
Check the assumptions and units before using this result. Read about calculation methods.