https://pokemongo.gamepress.gg/pokemon-stats-advanced
Stamina = (Base Stamina + Individual Stamina) * CP_Multiplier
You can see a pokemon's base stamina on the pokemon list or on that pokemon's page.
At level 40, CPM is 0.79030001, so the range in HP for all pokemon from 0 to 15 Stm IV is
15 * 0.79030001 ≈ 11.85