Enter the linear attenuation coefficient (1/cm) into the Half Value Layer Calculator. The calculator will evaluate the Half Value Layer. 

Half Value Layer Formula

The following two example problems outline the steps and information needed to calculate the Half Value Layer.

HVL = .693/u


  • HVL is the Half Value Layer (cm)
  • u is the linear attenuation coefficient (1/cm) 

To calculate the half-value layer, divide .693 by the linear attenuation coefficient.

How to Calculate Half Value Layer?

The following steps outline how to calculate the Half Value Layer.

  1. First, determine the linear attenuation coefficient (1/cm). 
  2. Next, gather the formula from above = HVL = .693/u.
  3. Finally, calculate the Half Value Layer.
  4. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

linear attenuation coefficient (1/cm) = .707

HVL = .693/u = ?