Enter the number of lone electron pairs on the central atom and the number of atoms bonded to the central atom into the Steric Number Calculator. The calculator will evaluate the Steric Number. 

Steric Number Formula

The following two example problems outline the steps and information needed to calculate the Steric Number.

SN = #LEP + #AB

Variables:

  • SN is the Steric Number ( )
  • #LEP is the number of lone electron pairs on the central atom 
  • #AB is the number of atoms bonded to the central atom 

How to Calculate Steric Number?

The following steps outline how to calculate the Steric Number.


  1. First, determine the number of lone electron pairs on the central atom. 
  2. Next, determine the number of atoms bonded to the central atom. 
  3. Next, gather the formula from above = SN = #LEP + #AB.
  4. Finally, calculate the Steric Number.
  5. 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.

number of lone electron pairs on the central atom = 5

number of atoms bonded to the central atom = 6

SN = #LEP + #AB = ?