Formula
- 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.
- Simple physical-decay age using supplied half-life. Not a calibrated calendar date; reservoir effects and laboratory conventions excluded.
Example Calculation
- Remaining activity: 50 %
- Assumed half-life: 5730 years
Remaining activity = 50; Assumed half-life = 5730. Primary result: 5730.
Frequently asked questions
How do I use this calculator?
Enter remaining activity, assumed half-life. The result updates automatically. Use Reset to restore the example values.
What method does it use?
age=−half-life ×ln(fraction)/ln2.. Simple physical-decay age using supplied half-life. Not a calibrated calendar date; reservoir effects and laboratory conventions excluded.
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.