The formula you’re looking for is: Round( CurrentHealth / MaxHealth * 100).
First get the percentage of current health compared to max health.
For example, 1000 current health divided by 2000 max health is 0.5.
Percentages are scaled from zero to one. To get it scaled from zero to a hundred we just multiply the number by a hundred.
0.5 times a hundred is 50.
Then, since you don’t want the fraction when dividing unequally (like 100 out of 300 is 33.33333etc) we round it so it becomes just 33.
This is how you would do it in BP:
