Bond order is a calculation to determine both the type and stability of a covalent bond. Bond order is applied to molecular orbital theory. The equation for calculating bond order is described below.

Any bond which has a bond order greater than zero is considered stable. Zero bond order bonds are unstable and do not exist. A bond order of 1 describes a single covalent bond, bond order of 2 describes a double covalent bond, a bond order of 3 describes a triple covalent bond, etc. A fractional bond order (like 1.5) may describe a molecule that exists, but the bond holding the two atoms together is reactive. Bond order is used to predict the energy bonding two atoms together in a molecule and the resulting bond length.