Radioactive Decay Calculator
Remaining activity after elapsed time, for common diagnostic and therapeutic isotopes
High-yield mode — key points, high-yield facts, tables & quizzes only. Toggle off for full text.
Activity decays exponentially: A = A₀ · e^(−0.693·t / t½). Enter a starting activity, choose the isotope, and set the elapsed time to find the remaining activity — useful for dose scheduling and decay correction.
Decay & hot-lab draw-back calculator
MBq
MBq/mL
MBq
Forward: A = A₀·e^(−0.693·t/t½). Draw-back: to deliver the desired activity after time t, draw more now (needed = desired ÷ decay factor); the volume uses the current stock concentration. Verify against your dose calibrator.
Evidence & sources
BRadioactive decay law — standard physics (A = A₀·e^(−0.693·t/t½)); isotope half-lives from reference data.