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Half Life Calculator

Select any parameter and the calculator will calculate its value by using the half life formula, with necessary parameters being provided.


Half Life, Mean Lifetime, and Decay Constant Conversion

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 An online half life calculator allows you to compute the remaining amount of an element after a certain period of time. Undoubtedly, calculating half life, mean lifetime, and decay constant is such a difficult and time consuming task, but thanks to half-life calculator that provide all these computation in a fraction of a second. This context shows the half-life definition, its formulas and the method of calculating half life.

What is Half Life?

Half-life is usually defined as the time needed by a radioactive substance (or half of its atoms) to decay or transform into another substance. This principle was first discovered in 1907 by Rutherford. It is usually identified by the symbol Ug. Or t1 / 2.

For better understanding, let's take the example of a radioactive element with one hour half-life. In this case, half will decompose within one hour, and the rest will decompose within another hour.

Reaction Half-Life:

The half-life of a chemical reaction can be defined as the time required for the concentration of a given reactant to reach 50% of its initial concentration (the time required for the concentration of a reactant to reach half of its initial concentration). It is represented by the symbol "t1 / 2", usually expressed in seconds.

Half Life Formulas:

Here are some half life equations are used by half life calculator for determining the half-life that are used to describe the decay in elements.

N(t) = N_o (½) t / t ½

N(t) = No e-t / r

N(t) = Noe– λt

Here we consider the following,

N_0 = the initial quantity of the substance

N(t) = the quantity that is left over

t1⁄2 = half-life

τ = mean lifetime of the decaying quantity

λ = decay constant

Timing Using Radioactive Decay:

The half life equation for calculating the elapsed time from the beginning of the decay process to the current moment, related to the beginning of the decay is calculated by using the half-life formula:

\(T = t_ {1 / 2} \dfrac{ln{N_{t}}{N_{0}}}{- ln \left(2\right)}\)


t = elapsed time

\(t_{\dfrac{1}{2}}\) = half-life of the particle

\(N_{0}\) = quantity at the beginning

\(N_{t}\) = quantity t changed over time

This equation is also used by half life calculator to find the time elapsed.

Half-Life, Decay Constant, and Mean Lifetime:

Radioactive decay is an exponential process, which means that the amount of matter decreases in proportion to its current value. The most intuitive mathematical description of decay rate is half-life, which can be calculated by our radioactive decay calculator. The Half life equation for the relation between the half-life, decay constant, and mean lifetime is:

\(t_{1/2} = \dfrac{ln\left(2\right)}{λ} = τ ln\left(2\right)\)


\(t_{\dfrac{1}{2}}\) = half-life of the particle

τ = half-life

λ = attenuation constant

ln = natural logarithm.

How to Calculate Half Life?

  • Determine the initial amount of an element, for example N (0) = 2.5 kg.
  • Determine the final quantity of an element, for example N (t) = 2.1 kg.
  • Measure the time required for that amount of substance to decompose. In our experiment, we found that it takes 5 minutes.
  • Enter these values ​​into the online half-life calculator. It provides the results quickly - in this case, the half-life is equal to 19.88 minutes.
  • If you are not sure whether our radioactive decay calculator gives the correct result or not, you can use the half-life equation to check the accuracy.

How does Half Life Calculator Works?

An online decay constant calculator displays the half-life of chemical substance with the following steps:


There are two different options are available for determine the half life and corresponding values:

Half-Life Calculations:

  • First, choose an option from drop-down list to find the half life, time, or initial and final quantity of any radioactive substance.
  • Then, substitute the given values in the related fields.

Mean Lifetime, and Decay Constant Conversion:

  • Select half life, decay constant, or mean lifetime from drop-down list and add the certain value.


  • The half life calculator displays step-by-step calculations for half life, time, initial and final quantity.
  • When you want conversions then it converts and show complete calculations for the given value into half life, mean lifetime, and decay constant.


What is radioactive decay?

Radioactive decay is a method in which unstable atomic nucleus lose energy (related to the mass in their rest frame) by generating radiation such as alpha particles, beta particles with neutrino, or a neutrino in the case of electrons capture, gamma rays or electrons when they are converted internally. Materials containing such unstable nuclei are considered radioactive. Some highly excited short-lived nuclear states can decay through the emission of neutrons or protons

How many types of Radioactive Half-Life Decay?

There are three types of radioactive half life decay

  • Alpha Decay
  • Beta Decay
  • Gamma Decay

What is the half life of carbon 14?

The carbon 14 has a half-life of 5730 ± 40 years.

How does Radioactivity works?

The atom of the heavier element does not have an ideal proton/neutron ratio. This makes them unstable. To approach a stable ratio, atoms go through radioactive decay and in the process releasing energy or various particles as by-products.


Use this online half life calculator that allows you to understand the principles of radioactivity decay and an easy way of calculating half life, the initial and final quantity of an element, or its decay constant. A half-life generally describes the decay of discrete substances, such as radioactive particles. Generally, half life is defined in the terms of probability. The radioactive decay calculator is used to saves a lot of time doing manual calculations of half life.


From the source of Wikipedia: Half-life, Probabilistic nature, Formulas for half-life in exponential decay, Half-life and reaction orders, Decay by two or more processes.

From the source of Leuman Learning: Activity, the Rate of Decay, Human and Medical Applications, MASS OF Cs137 ESCAPED CHERNOBYL.

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