Originally Posted by
Frannibal
Is it frowned upon ...
That probably depends on who you ask. But on finals with a crosswind landing ahead there are more important things to do than look up the exact value of the crosswind component from a chart. The wind speed and direction they give you are only approximat values anyway, so what's the point of deriving "exact" values from them using charts (or even worse: a calculator or smartphone app - yes those exist as well...)? Listen to your instructor I would say and estimate it using some rule of thumb!