Activity at a Specific Date/Time
Tell us when you measured it and the exact time you care about. We’ll handle the decay in between.
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Examples: Tc‑99m (6 h), F‑18 (110 min), I‑131 (8 d).
Enter the value exactly as shown on your readout and its unit.
Use your local date/time. If unsure, click Now and adjust.
Pick any future/past time. We’ll calculate the time difference automatically.
Your result will appear here.
What’s happening under the hood?
We compute the elapsed time between your two date/times and apply
A(t) = A₀ · e^{−λt}
with λ = ln(2)/T½
. Times are handled using your browser’s local timezone.