Hitpoints

Hitpoints are the amount of damage after all reductions that a unit has to take before it dies, hence why they are one of the most important things in game.

There are plenty of factors that decide your amount of max hitpoints in the game

• Your base hitpoints (For all heroes in DotA it’s 150)
• Your total Strength (because every point in STR gives 19 HP)
• Some skills or items that provide a direct increase in Hitpoints (like a Soul Booster)

Besides dealing damage there are some skills that reduce your amount of hitpoints (which means they are not reduced by anything) these are:

     Burning Spear (to Huskar)
     Icarus Dive (to Phoenix)
     Fire Spirits (to Phoenix)
     Sun Ray (to Phoenix)
     Sunder
     Nightmare (except fatal damage)
     Heartstopper Aura (except fatal damage)
     Fatal Bonds (except fatal damage)
     Overcharge (to Io)
     EMP (except fatal damage)
     Wave of Terror (except fatal damage)
     Soul Ring (cannot be fatal)
     Urn of Shadows (except fatal damage)

Regenerating Hitpoints

Hitpoints can, of course, be recovered if you lose some, you can recuperate them via spells or consumables and by natural regeneration.

Hitpoints Regeneration Per Second:

HP regenerated per second = Base Hitpoint Regeneration + (Strength * .03) + (Bonus HP Regen from Items and Skills)

Where:

Base Hitpoint Regeneration: It's a value set by the mapmaker in the WC3 Editor, for most heroes in DotA it's 0.25 (Exceptions: Nerubian Assassin has 2.5, Axe has 2, Gondar, Faceless Void, Juggernaut, Krobelus, Naga Siren, Spiritbreaker, Stealth Assassin, Venomancer, Pandaren Brewmaster and Phantom Lancer have 0.75, Shadow Fiend and Lone Druid have 0.5, Alchemist while using Chemical Rage has 15/30/60)
Strength: Total STR including the green numbers

Note that the regen granted by Heart Of Tarrasque is only MAX_HP*0.02 added to the result of this formula.

Example:

Axe with 35+10 STR with two ROR
Total=1+(45*0.03)+(2+2)
Total=1+1.35+4
Total=6.35 HP/Sec

Mana Points:

Mana is the component that allows the heroes to cast most of the spells, without mana a Caster hero is almost rendered useless.

The factors that determine your amount of Mana are:

• Your base mana (For all the heroes in DotA is 0)
• The amount of INT you have, since each point of INT gives 13 mana points
• Some items like the Energy Booster that increases Mana Points directly

Some skills reduce Mana Points directly, such as

• Feedback, which on every attack reduces the amount of Mana Points of the target
• Mana Burn, which burns mana dealing damage along.
• Nether Ward, which has an aura that reduced mana regeneration
• Mana Leak, which substracts mana based on distance moved while affected by it

But like Hit Points, Mana can be replenished with consumables, some skills and naturally by regeneration.

Mana Regeneration:

Mana regenerated per second=[Base Mana Regen + (Intelligence* .04)] * [1 + (% Total Percentage Increase)] + Regeneration From Brilliance Aura

Where:

Base Mana Regen: Is a value set by the mapmaker in the WC3 Editor, for all heroes in DotA it's 0.01 (Except Techies who has 0.02 and Alchemist in Chemical Rage, who has 3/7.5/12 depending on the level)
Intelligence: It's your amount of INT including the amount in green numbers
Total Percentage Increase: Is the sum of all bonus percentages, in the example of one Sobi Mask (50%) and one Refresher Orb (200%) we display the result as 2.5
Regeneration From Brilliance Aura: The fixed amount granted by Brilliance Aura, note that it comes after every other increase so it doesn't affect the percentages at all.

Example:

     Alchemist with 30+15 INT using:
     Chemical Rage Lvl2
     2x Battlefuries
     1x Ring Of Basilius
     Crystal Maiden's Aura Level 2

Total=[7.5+(45*0.04)]*[1+(1.5+1.5)]+0.65+1.0
Total=9.3*4+1.65
Total=37.2+1.65
Total=38.85