Half-Life Calculator (Radioactive Decay)

Science Tools

Amount left after radioactive decay

FreePrivateInstant
Starting amount
Half-life
Elapsed time
Full guide, 4 min readHalf-life: why things fade by half, again and again, and never quite reach zeroRead the story behind this tool →
Embed this tool on your websiteFree
  1. Choose how tall the frame should be.
  2. Press Copy code.
  3. Paste it into your page, blog, WordPress or Notion HTML block.
Height
Live previewAll embeddable tools

The tool runs inside your visitor's browser, nothing is uploaded, and a small "Powered by ToolCloak" line stays under it. The second line (script) is optional: it makes the frame fit the tool's height.

Similar tools you may like

Lumpsum Investment CalculatorFuture value of a one-time investment
pH Calculator (pH, pOH, H+ and OH-)Convert between pH, pOH, [H+] and [OH-]
Projectile Motion Calculator (Range, Height, Time)Range, max height and flight time of a projectile
Days Until CalculatorDays left until a date
Digit Sum & Digital Root CalculatorSum, product and digital root of the digits of a number
Discount CalculatorSale price after discount & how much you save

History

All history →

Half-Life Calculator (Radioactive Decay) — at a glance

Start amount, half-life and time give what is left.

Your values
100 g
half-life 5 years
15 years
Calculate
Result
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.

More Free Tools

Guides you might like

All guides →
Projectile Motion Calculator (Range, Height, Time)Projectile motion: why 45 degrees throws farthest (and when it does not)
Ohm’s Law Calculator (Voltage, Current, Resistance, Power)Ohm's law explained: volts, amps, ohms and watts with worked examples
Final Grade CalculatorFinal grade calculator: how to find the score you need on the final exam to reach your target grade
Speed, Distance & Time CalculatorSpeed, distance and time calculator: how to find speed, distance or travel time, and why average speed is not a simple average