Defensive CR: HP 202 gives base defensive CR 9, increased to 10 for AC 18
Offensive CR: 102 dpr gives base offensive CR 16; attack +9 is no adjustment.
Final CR: 13
Blue Dragon (CR 16)
Defensive CR: effective HP 302 (212 base, +90 for legendary resistance) gives a base defensive CR of 16; AC and saves have no effect.
Offensive CR: 157 dpr (assumes, over 3 rounds breath hitting 2 targets, 5x shatter hitting 10x, 10x rend) gives a base of 21, attack +12 is no effect
Final CR: 18.
Pit Fiend (CR 20)
Defensive CR: effective HP 457 (337, +120 for legendary resistance) is base 22. AC 21 (expected 19) is +1. Magic resistance is +2 AC or another +1. Total 24.
Offensive CR: 122 dpr (assumes hellfire spellcasting once, two multiattacks, and two poison tics) is base 19. Attack +14 boosts that to 21.
Final CR: 22
Ancient Red Dragon (CR 24)
Defensive CR: effective HP 627 (507 base, +120 for legendary resistance) is base 26; AC 22 (expected 19) is +1.
Offensive CR: 204 dpr (assumes breath hitting 2 targets, 15x rend) is base 24, attack bonus +17 boosts that to 26.
Final CR: 26
Not sure if they changed budgets, changed base numbers, or are ignoring some factor.
Did some math on a couple examples
Not sure if they changed budgets, changed base numbers, or are ignoring some factor.
Where are the new rules for calculating CR? Do they expect people to buy the old DMG too?
The new rules for calculating CR are... not published.