Bond Order Calculator
Determine the bond order of a diatomic molecule by counting bonding and antibonding electrons from its molecular orbital (MO) diagram.
Triple bond (strongest common bond)
- 1
Net bonding electrons = bonding − antibonding
8 − 2 = 6 - 2
Bond order = net bonding ÷ 2
6 ÷ 2 = 3
How does this calculator work?
Bond order = (bonding electrons − antibonding electrons) / 2, derived from the molecular orbital diagram. Bond order 1 = single bond, 2 = double, 3 = triple; fractional values (e.g., 2.5 for NO) arise from unpaired electrons in partially filled orbitals. Higher bond order → shorter, stronger, higher-energy bond.
Formula
How this is calculated
In molecular orbital theory, electrons fill delocalized orbitals that span the whole molecule rather than sitting between individual atoms. Bonding MOs (σ, π) lower the system energy and hold atoms together; antibonding MOs (σ*, π*) raise energy and weaken the bond. Dividing the net number of stabilizing electrons by two — because a full covalent bond requires an electron pair — gives the bond order.
Bond order predicts key physical properties: higher bond order means a shorter, stronger, and higher-energy bond. Bond order 1 is a single bond (H₂, F₂), 2 is a double bond (O₂), and 3 is a triple bond (N₂). Fractional values arise from partially filled orbitals: NO has bond order 2.5 because it has one electron in a π* orbital. A bond order of 0 means the molecule is too unstable to exist under ordinary conditions (e.g., He₂).
To use this calculator, fill the MO energy diagram for your molecule in ascending energy order (σ1s, σ*1s, σ2s, σ*2s, σ2p or π2p — see your textbook for the ordering, which differs between O₂/F₂ and lighter diatomics), then count bonding and antibonding electrons separately. The formula is exact for homodiatomic molecules and a reliable approximation for simple heterodiatomics.
Frequently asked questions
A fractional bond order means an electron occupies a partially filled bonding or antibonding orbital unpaired. NO (bond order 2.5) is a classic example. Fractional bond orders still correlate with shorter and stronger bonds compared to the next lower integer order.
Fill the MO energy diagram using the Aufbau principle and Hund's rule. Electrons in σ and π orbitals are bonding electrons; electrons in σ* and π* orbitals are antibonding. Count the totals for each group separately.
Bond order and bond energy are directly proportional; bond order and bond length are inversely proportional. N₂ (bond order 3) has a bond energy of ~945 kJ/mol and a length of 110 pm; F₂ (bond order 1) has ~159 kJ/mol and 142 pm.
TG we-Calculate Editorial Team. (2026). Bond Order Calculator [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/bond-order-calculator
TG we-Calculate Editorial Team. "Bond Order Calculator." TG we-Calculate. 2026. https://we-calculate.com/calculator/bond-order-calculator.
TG we-Calculate Editorial Team, "Bond Order Calculator," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/bond-order-calculator
@misc{wecalculate_bond_order_calculator, title = {Bond Order Calculator}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/bond-order-calculator}}, year = {2026}, note = {TG we-Calculate} }
Did this calculator help you?