The mapping of PC Level to Monster CR is...convoluted. It's not exactly linear because there are a handful of power spikes on both sides. It is also different between 2014 and 2024. It is roughly (in 2024):
Lvl CR
1 1/2
2 1
3 1.5
4 2.2
5 4
6 4.6
7 5
8 6
9 6.5
10...
Hey Mike, as someone who tried reverse engineering an encounter building point system, I can warn you away from a pitfall I fell into.
Essentially, increasing a monster by 1 CR makes a monster ~50% more dangerous at low levels but only ~10% more dangerous at high levels (those number values are...