Created By : Rina Nayak

Reviewed By : Phani Ponnapalli

Last Updated : May 19, 2023

Given Half-Life Calculator is useful to find the half-life, decay constant, initial and final amount of substance easily. Just provide inputs i.e initial quantity, final quantity, total time and click the blue colour calculate button to check the half-time in a less amount of time.

Initial Quantity(N(0))
Half-life time (T)
Total time
Remaining quantity (N(t))
Decay constant (λ)
Mean Lifetime(τ)

Step by Step Process to Find Half-Life

Check out the simple steps to calculate the radioactive substance half-life.

  • Obtain the initial quantity, total time and final quantity of the substance.
  • Place the values in the Half-life formula.
  • Solve the equation for the half-life to get the result.

What is the Half-Life?

Half-life is a phenomenon that takes place daily in various chemical reactions and nuclear reactions. It is the amount of time it takes for half of a particle sample to react. In nuclear physics, the half-life represents the time taken by atoms to undergo radioactive decay.

Every atom has a different half-life. For example, uranium-233 has a half-life of 160,000 years. It is used to describe a kind of exponential decay. The half-life is a probabilistic measure and it can't give the exact half of the substance that will be decayed after the time of half-life has elapsed.

Half-Life Formula

The number of unstable nuclei remaining after the time can be find using the Half-life formula

N(t) = N(0) x 0.5(t/T)

N(t) = N(0) x e(-t/τ)

N(t) = N(0) x e(-λt)


N(t) is the remaining amount of a substance after time t has elapsed

N(0) is the initial amount of the substance

T is the half-life

t is the full time

τ is the mean life time that is the average amount of time a nucleus remains intact

λ is the decay constant


Question: Calculate the half-life of a radioactive substance whose disintegration constant is 0.002 1/years?


Given that,

Radioactive constant λ = 0.002 1/years

Half-life t½ = 0.693/λ

= 0.693/0.002

= 346.5 years

Therefore, the radioactive substance half-life is 346.5 years.

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FAQ’s on pH Calculator

1. What is meant by half-life?

Half-life is nothing but the time required for a quantity to reduce to half of its initial value. It is generally used in nuclear physics to know how quickly unstable atoms will undergo radioactive decay.

2. How to calculate the half-life without a calculator?

Determine the initial quantity, final quantity of the substance, total time. Substitute these values in the half-life equation and solve to get the half-life of the substance.

3. What is a Half-life formula?

The number of unstable nuclei remaining after the time t can be calculated using the half-life equation. It is N(t) = N(0) x 0.5(t/T). Here, N(0) is the initial quantity of the substance, N(t) is the remaining quantity of the substance after t time, T is the half-life.

4. Calculate the half-life of a radioactive substance whose disintegration constant is 0.004 1/years?

Given that,

The decay constant of the radioactive substance = 0.004 1/years

The half-life formula is t½ = 0.693/λ

= 0.963/0.004

= 173.25

Therefore, the half-life of the radioactive substance is 173.25 years.

Half-Life Calculator