I was curious about this because I know that having a pokémon at the max dynamax level doubles the hp. Is there an equation to determine the hp? Thanks in advance!

Here is the calculation for Dynamax Pokémon's HP:

Level 0 = 1.5 Level 1 = 1.55 Level 2 = 1.6 Level 3 = 1.65 Level 4 = 1.7 Level 5 = 1.75 Level 6 = 1.8 Level 7 = 1.85 Level 8 = 1.9 Level 9 = 1.95 Level 10 = *2

Source

Without any Dynamax Candies, a Pokémon receives 1.5x health when it Dynamaxes. That multiplier gets 0.05 added for each Dynamax candy. So a Pokémon with a Dynamax Level of 5 has its HP boosted by 1.5+(0.05*5) = 1.75x.