How many "hit points" is a single heart worth?
Solution 1:
Each quarter heart is worth 1 HP. This means one heart is worth 4 HP, and once you max out your health capacity, you end up with 120 HP (30 hearts).
This might not sound like much, but remember that you have some damage mitigation that most enemies don't have. As detailed in this answer, each point of armor you have reduces incoming damage by 1 HP (1 quarter heart), and defense elixirs can add up to 24 armor to your stats. The fact that you can stop a battle to eat a four course meal also helps keep your health up.