Decay Calculator — Activity at Time t
Fill the boxes exactly as described. No physics jargon needed.
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Example: Tc‑99m for most nuclear med elution/activity checks, F‑18 for PET, etc.
Put the value you actually read at the time of measurement. Choose the unit that matches it.
Example: if you measured A₀ at 08:00 and now it’s 14:00, enter 6 and choose hours.
This does not change the calculation — only how the result is shown.
Your result will appear here.
What’s happening under the hood?
We use the standard decay formula
A(t) = A₀ · e^{−λt}
with λ = ln(2)/T½
from the isotope list.
You tell us A₀ (at the time you measured it) and how much time has passed. We give you the activity now.