Enter an initial quantity, a half-life duration, and an elapsed time to find how much remains. Everything runs in your browser — nothing you enter here is uploaded, stored, or logged.
Calculated locally in your browser — nothing is sent to our server.
How This Calculation Works
Half-life describes exponential decay: after each half-life period, half of the remaining quantity decays. The formula is N(t) = N₀ × (1/2)^(t ÷ half-life). The half-life and elapsed time must be entered in the same time unit (for example, both in years, or both in days) — this calculator does not convert between units automatically.
FAQ
What units should I use?
Any consistent unit works, as long as the half-life and elapsed time are both in that same unit — for example, both in years.
Is my data uploaded anywhere?
No. The calculation happens entirely in your browser using JavaScript.