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.
- Illustrative decay curve only. The half-life is supplied, not a validated prediction of anyone’s memory. Relearning and individual differences are excluded.
Example Calculation
- Initial retained amount: 100 %
- Elapsed time: 10 days
- Assumed retention half-life: 10 days
An assumed ten-day half-life turns an initial 100% into 50% after ten days.
Frequently asked questions
How do I use this calculator?
Enter initial retained amount, elapsed time, assumed retention half-life. The result updates automatically. Use Reset to restore the example values.
What method does it use?
retained=initial × 2^(−time/half-life).. Illustrative decay curve only. The half-life is supplied, not a validated prediction of anyone’s memory. Relearning and individual differences are 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.