Calculate half-life and remaining quantity for first-order decay or reaction.
Each half-life removes half of whatever remains, so decay is exponential rather than linear. Reaching one per cent takes about 6.6 half-lives, which is the practical definition of complete decay. Half-life is independent of starting quantity for first-order processes, which is what makes radiometric dating possible.
Half Life Reaction
N = N₀ × (½)^(t/t½); k = ln2 ÷ t½
N = N₀ × (½)^(t/t½); k = ln2 ÷ t½ Each half-life removes half of whatever remains, so decay is exponential rather than linear. Reaching one per cent takes about 6.6 half-lives, which is the practical definition of complete decay.
Half-life is independent of starting quantity for first-order processes, which is what makes radiometric dating possible.
This calculator takes 3 inputs: Half-life, Time elapsed, Initial amount. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.