Personally I don't do any calculations per say but I do pay attention to direction.
Telltale signs:
Flags are a big clue but also dust/leaves/debris kicked up by the wind is another.
You know those tiny 2 inch marker flags? I use them as "Wind socks" as well.

The roads around here are really twisty turny in practically all directions so I'm always looking for those signs on a given segment.

If I have a general tail wind I usually have a choice of either:
A. Drive a little faster and still reach my MPG goal
B. Still drive like I'm on my last fumes and have a great chance at a really good run. (I choose this one)

If I have a strong cross wind I'll really go more extreme and watch every move I make and be sure what ever I do has a reason.
Same thing with a head wind but in that case I'll just take it slower so the wind doesn't slam & plow so much.
If a freeway truck, especiall those two trailer FedEx types are going about my speed I'll slip behind at a safe, comfortable distance (100-200' @ 52-55MPH) and let their wake screw up the headwind.
If the two of us are heading up a hill and he isn't driving with the load I'll be thankful of him and begin to drop back.

I also duck & cover by exiting the "naked" freeway and seek the sideroads where trees, buildings etc break the wind. Every once in a while I'll find a strong venturi effect but I get that on the freeway too, especially as I reach the top of hills.

We've just gone through a 4-5 day wind storm where things are great on the first half of my commute but terrible going back, the wind blew all night.
I had to take it much slower and exit the freeway sooner. It took 10-15 minutes more to get home.....1hr 20min to go 46 miles and I haven't calculated my average speed but I'll tell you it is way too slow for my tastes.

But...I can also tell you that I parked with at least 68MPG on the dash for the trip
which would otherwise been a complete disaster.
I'm over 600 miles and slightly more than half tank left. I'm so glad I took it slower.