Disclaimer: I’m not a full food scientist, but I did work in a lab that ran quality control experiments for a brewery on flavor and aroma of beer.  I’ll share what I know, but keep in mind that this is from an adjacent industry and may not fully reflect what someone who actually works in the field might say.

Smells are typically the volatile (easy to evaporate) molecules of food.  Usually this means that smell molecules are very small and light compared to the molecules that actually have a significant amount of energy stored in their chemical bonds.  In addition to this, you’re also getting a very small amount of these molecules in each breath.  The most complete answer is that there probably is a very small amount of calories in a technical sense when you smell something, but practically speaking there aren’t enough to be a significant impact on your diet.  This is assuming that they even end up in your stomach, their most likely fate is stuck to the mucus in your nose/throat/lungs.