Science calculator
Half-life and decay.
Enter any three of initial quantity, remaining quantity, elapsed time and half-life. Use particle count, amount or activity consistently.
Remaining quantity NSolved
—
N = N₀(½)^(t/T½)
- Fraction remaining
- —
- Quantity decayed
- —
- N₀ initial amount or activity · N remaining amount or activity · t elapsed time · T½ half-life
Assumptions
- One radionuclide with a constant decay probability and a fixed half-life.
- No new nuclei are produced and no daughter activity is added.
- Initial and remaining entries use the same kind of quantity and compatible units.
- For activity, any background count rate has already been removed and detector response is unchanged.
How it works
After each half-life, half of the undecayed nuclei remain. Three half-lives therefore leave one eighth of the initial quantity.
Activity is proportional to the number of undecayed nuclei for a single isotope, so it follows the same fractional law. It can be used in place of N when units are kept consistent.
Leave one field blank to solve it. The logarithmic rearrangements for elapsed time and half-life assume 0 < N ≤ N₀.
- Free
- No ads
- No tracking
- No account
- Works offline once loaded
From the maker of Ans — a scientific calculator you can own. Same idea: a proper instrument, nothing in the way.