Zorgoth.com
Science
Radioactive Decay
Calculator
Calculate remaining activity and decay time for radioactive isotopes. Uses the standard decay formula N(t) = N₀ × (1/2)^(t/t½).
Isotope (or enter custom half-life)
Custom
Carbon-14 (5,730 years)
Uranium-238 (4.47 billion years)
Radium-226 (1,600 years)
Caesium-137 (30.17 years)
Iodine-131 (8.02 days)
Plutonium-238 (87.74 years)
Thorium-232 (14.1 billion years)
Radon-222 (3.82 days)
Tritium / H-3 (12.3 years)
Americium-241 (432.2 years)
Half-Life
years
days
hours
minutes
seconds
Initial Amount (N₀)
units
grams
mol
Bq
Ci
Elapsed Time
years
days
hours
minutes
seconds
Decay Table (every half-life)