Armor damage reductions for each class

With the new chemist testing I've seen a lot of people confused about how much more damage chemist takes now than before, and about how much damage things do in general. I've decided to create this guide to how much damage is reduced by each class' armor, according to https://minecraft.gamepedia.com/Armor/Before_Java_Edition_1.9. To sum, briefly: Each armor point reduces incoming damage by 4%. Each protection enchantment reduces incoming damage according to its EPF. The EPF is capped at 25, multiplied by a random number between 0.5 and 1, and capped at 20. Damage is then reduced by 4% per EPF, however this reduction takes place after it it reduced by armor. The formula for finding the damage reduction in this case is (1-armor reduction)*(1-enchantment reduction)=(1-total reduction).

Heavy
Heavy has 20 armor points for 80% damage reduction.

Archer
Archer has 12 armor points for 48% damage reduction.

Medic
Medic has 11 armor points for 44% damage reduction.

Soldier
Soldier has 15 armor points for 60% damage reduction.

Assassin
Assassin has 1 armor point for 4% damage reduction.

Old Chemist
Old Chemist had 10 armor points for 40% damage reduction. Additionally, resistance I gives it an additional 20% damage reduction that takes place after the armor reduction like enchantments. This gives it a sum of 52% damage reduction.

New Chemist
New Chemist has 10 armor points for 40% damage reduction. Additionally, it has two pieces with protection I for 2 EPF. Applying multiplication by a number between 0.5 and 1 makes this 1-2 EPF, however since the value is then rounded up it will be 2 99% of the time. This gives it 8% damage reduction and rarely 4% damage reduction. This gives it 44.8% damage reduction, or rarely, 42.4% damage reduction.

Dwarf
Dwarf has 17 armor points for 68% damage reduction.

Elf
Elf has 6 armor points for 24% reduction. Additionally, it has one piece with Prot III and two with prot II for an EPF of 7. Multiplying it by 0.5-1 and rounding, it can be 4-7 for a damage reduction of 16-28%. This gives it a total damage reduction of 36.16%-45.28%.

Engineer
Engineer has 9 armor points for 36% reduction. Additionally, all pieces have prot I for an EPF of 4, which becomes 2-4 EPF for 8%-16% damage reduction. The total damage reduction is 41.12%-46.24%

Mage
Mage has 6 armor points for 24% damage reduction. Additionally, it has 1 piece with prot II giving it 2 EPF. Like chemist, this becomes 2 EPF or very rarely 1 EPF for a reduction of 4-8%. It has a total damage reduction of 27.04%-30.08%.

Necro
Necro has 14 armor points for a damage reduction of 56%.

Ninja
Ninja doesn't have any damage reduction.

Pyro
Pyro has 10 armor points for a damage reduction of 40%.

Scout
Scout has 2 armor points for a damage reduction of 8%. Additionally, it has prot 1 for 1 EPF (which can only be 1 EPF even if multiplied by 0.5) and 4% damage reduction. In total it has 11.68% damage reduction.

Fashonista
Fashionista has 7 armor points for a damage reduction of 28%.

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Charted:

 

Part 2: Effective Health

Using the formula Ivan suggested: health = (20 + 8 * amount of steak) / (1 - damage reduction) with one exception to be explained.

Heavy has 20 + 24 health from steak and a 80% damage reduction for 220 effective health.

Soldier has 20 + 32 health from steak and a 60% damage reduction for 130 effective health.

Medic has 20 + 48 health from steak and a 44% damage reduction for 121.43 effective health.

Archer has 20 + 32 health from steak and a 48% damage reduction for 100 effective health.

Assassin has 20 health and 4% damage reduction for 20.83 effective health.

Old Chemist has 20 + 60 health from pots and 52% damage reduction for 166.67 effective health.

New Chemist has the same amount of health but 44.8% damage reduction for 144.93 effective health.

Dwarf has 20+24 health from steak and 68% damage reduction for 137.5 effective health.

Elf has 20+40 health from steak and 45.28%-36.16% damage reduction for between 109.65 and 93.98 effective health.

Engineer has 20+40 health from steak and 46.24%-41.12% damage reduction for between 111.61 and 101.90 effective health.

Mage has 20 health and 30.08% damage reduction for 28.60 effective health, however with proper heal spell timing, it can have an infinite healthpool.

Necro has 20+32 health from steak and 56% damage reduction for 118.18 effective health.

Ninja has 20 health.

Pyro has 20+32 health from steak and 40% damage reduction for 86.67 effective health.

Scout has 20+16 health from steak and 11.68% damage reduction for 40.76 effective health.

Fashionista has 20+48 health from steak and 28% damage reduction for 94.44 effective health.

Ranked:


Charted:

 

It would be really hard to calculate regen as regen is time dependent. I think it does make a bit of difference for medic, engineer, and chemist but not so much for elf and ninja since it's hard for them to use their regen in a fight. Overheal is also tough to deal with as it depends on the skill of the necro or assassin.