@
Salamandrine, those calculators are useful. I would just not look at them as producing the best possible answer. And it takes a lot of work to measure and put in the numbers.
Guru fitters have their problems, too. I suspect they make assumptions about the rider, how much they want to exert themselves, how fast they want to go, etc. If you want to ride an omafiets, for example, a guru fitter is probably going to mislead you.