Half-Life Calculator

Half-life is the time required for a quantity to reduce to half its initial value. This calculator determines how much of a radioactive substance remains after any given time, or calculates the time needed to reach a specific remaining amount.

1. 1

   Enter Initial Amount

   Input the starting quantity of the substance

2. 2

   Enter Half-Life Period

   Input how long it takes for half the substance to decay

3. 3

   Enter Elapsed Time

   Input the time that has passed since the start

4. 4

   View Results

   See remaining amount, percentage remaining, decay constant, and number of half-lives elapsed

• 1

  Carbon-14 has a half-life of 5,730 years, useful for dating organic materials up to 50,000 years old

• 2

  Uranium-238 has a half-life of 4.5 billion years, used for dating very old rocks

• 3

  After 10 half-lives, less than 0.1% of the original substance remains

• 4

  Half-life is constant and independent of the initial amount

• 5

  Nuclear half-life cannot be changed by temperature, pressure, or chemical reactions

• Thinking half-life means the substance is completely gone after two half-lives

• Confusing half-life with average lifetime (they differ by a factor of ln(2))

• Assuming environmental factors can change nuclear half-life (they cannot)

• Applying half-life calculations to non-exponential decay processes