Radioactive Decay Calculator

Find the amount remaining and decay constant.

Amount remaining 70.711

Decay constant (λ) (1/time) 0.0001

Percent remaining (%) 70.711

Formula: N = N₀ · e^(−λt), λ = ln2 ÷ half-life

Step-by-step with your numbers:

1. Values used:

2. Initial amount = 100

3. Half-life = 5,730

4. Elapsed time = 2,865

6. Amount remaining = 70.711

7. Decay constant (λ) = 0.00011/time

8. Percent remaining = 70.711%

Did we solve your problem today?

Model exponential radioactive decay using the decay constant.

The math behind it

λ = ln(2) ÷ half-life; N = N₀ × e^(−λt). Use consistent time units.

100 over half a half-life → ~70.7 remaining.

Vs half-life calc?

Same physics — this also reports the decay constant λ.