How do protections work?

In Smite, certain items grant magical or physical protection. Every mythological character has some degree of natural physical protection. Mages also get natural magical protection (while other chars don't). What does protection do? How (much) does it mitigate incoming damage?

A god's magical and physical protection values will reduce the amount of damage the corresponding types of damage apply. A god's inherent protections scale with level. For example, Ymir's total physical protection is 23 + 3.3 × level + Physical Protection From Items. Ignoring penetration for now, the formula is:

Actual damage = (unmitigated damage × 100)/(100 + protection value)

The result of this equation means that a protection value of 50 will reduce damage by 33%, 100 will reduce it by 50%, and 150 will reduce it by 60%.

For example (still ignoring penetration), if Ra's Celestial Beam is listed as doing 400 damage, and he hits someone with 70 magical protection, then the actual damage will be (400 × 100)/(100 + 70) = 235.

http://smite.gamepedia.com/Damage#Defense_and_Mitigation

It can also be though of 1 protection as 1% extra max HP against that damage as 100 protection mitigates 50% of that damage. So if someone had 100 health and 100 protection they really have 200 health to that type of damage.

(Max HP)*(1+(Protections/100))