What is the formula for calculating the bond order?

Bond order is given by

Bond order = [number of bonding electrons – number of anti-bonding electrons]/2

Bond order is directly proportional to bond dissociation energy and inversely proportional to bond length i.e. higher the bond order, larger is the bond dissociation energy and smaller is the bond length.
Bond order gives an indication to the stability of a bond.

If the bond order is 1, 2, 3 the respective bonds will be single, double or triple bond.

Calculating the bond order of hydrogen molecule:
The electronic configuration of H₂ molecule is: σ (1s) ²
Therefore, number of bonding electrons =2
Number of anti-bonding electrons= 0
Hence the Bond order = 1(2-0) /2= 1
This means the two hydrogen atoms are bonded together by a single bond.