Radioactive Half-Life Calculator
Find how much of a decaying substance remains after a period of time, given its half-life. Enter starting amount, time elapsed and half-life to see…
8 of 8 free uses remaining today
Find how much of a decaying substance remains after a period of time, given its half-life. Enter starting amount, time elapsed and half-life to see amount remaining when you calculate.
Worked example
Example calculated from the starting values. Enter your own values and press Calculate to get your result.
With the default inputs (starting amount = 100, time elapsed = 10 years, half-life = 5 years), the results are: amount remaining 25.000.
Quick reference: starting amount vs result
Reference table based on the example values; it is not your calculation result.
| Starting amount | Amount remaining |
|---|---|
| 50 | 12.500 |
| 100 | 25.000 |
| 200 | 50.000 |
| 500 | 125.000 |
| 1,000 | 250.000 |
| 2,000 | 500.000 |
Frequently asked questions
What formula does this calculator use?
Amount remaining = n0 × pow(0.5,t ÷ hl). Variables: n0 = starting amount, t = time elapsed in years, hl = half-life in years.
What do I need to enter?
You need starting amount, time elapsed (years), half-life (years). Results update as you type.
What is an example result?
With the default inputs (starting amount = 100, time elapsed = 10 years, half-life = 5 years), the results are: amount remaining 25.000.
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