B-F bond order in BF₃ is:

Due to $\mathrm{p\pi }-\mathrm{p\pi }$ back bonding, BF₃ is a resonance hybrid and forms three resonating structures.

Bond order is determined as:

$\begin{array}{ccc}\mathrm{Bond} \mathrm{order}& =& \frac{\mathrm{Number} \mathrm{of} \mathrm{bonds} \mathrm{present} \mathrm{between} \mathrm{atoms}}{\mathrm{Total} \mathrm{number} \mathrm{of} \mathrm{resonating} \mathrm{structures}}\\ & =& \frac{4}{3}\\ & =& 1.33\end{array}$