How to calculate a rough estimate for the volume of a nitric oxide molecule? I was wondering what would be the best way to calculate a rough estimate for size of a nitric oxide molecule to use in comparison to a box. 

I was thinking volume would be the best method, but this gave me an answer in dm3/mol which I can't use for comparing against the volume of a box.
Take the volume per mole value (b) from a van der waals constants table (0.0289 L/mol) and divide by $6.022 \times 10^{23}$ molecules per mole.

This will give you a volume that you can compare to the box.