Half-Life Calculator

Find the amount remaining after radioactive decay.

Amount remaining 25

Percent remaining (%) 25

Half-lives elapsed 2

Formula: remaining = initial × (1/2)^(time ÷ half-life)

Step-by-step with your numbers:

1. Values used:

2. Initial amount = 100

3. Half-life = 5,730

4. Elapsed time = 11,460

6. Amount remaining = 25

7. Percent remaining = 25%

8. Half-lives elapsed = 2

Did we solve your problem today?

Half-life is the time for half of a substance to decay.

The math behind it

remaining = initial × (1/2)^(time ÷ half-life).

100 over 2 half-lives → 25 (25%).

Use the same time units

Half-life and elapsed time must share units.