Half-Life Calculator (Radioactive Decay)
Science ToolsAmount left after radioactive decay
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All history →Half-Life Calculator (Radioactive Decay) — at a glance
Start amount, half-life and time give what is left.
100 g
half-life 5 years
15 years
Calculate
12.5 g left
How to use it — step by step
Just your input — nothing to install or sign up for.
1
Enter your values
Fill in the boxes. Sample values are already there so you can see how it works.
2
Calculate
Press the button to get your answer instantly.
3
Read the result
The main answer is shown in a large card with extra details below it.
4
Copy it
Use the copy button to save the result anywhere.
Pro tips
Small things that make the result better.
✦Use the same time unit for the half-life and the elapsed time.
✦After 10 half-lives about 0.1% of the original amount is left.
Quick facts
Freeno signup, no limit
Instantresult in a moment
Privatenothing is uploaded
Any devicephone, tablet or PC
Frequently Asked Questions
Is my data safe?+
Yes. Everything runs inside your own browser. Your text, files and images are never uploaded to any server.
Is this tool really free?+
Yes — completely free, no signup, no watermark and no usage limit.
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