Dota-Allstars Spell Resistance Guides

Dota-Allstars Spell Resistance Guides will be posted here. This guide is made by gradenko_2000 from www.dota-allstars.com , all the credit belong to him.

Spell resistance in DotA is a beautiful thing. It lets you take more of those nasty nukes flying towards your face and last longer in the battlefield.

They're offered in three flavors:
Cloak of the Planeswalker, which gives 15% more resistance
Hood of Defiance, which gives 30% more resistance (among other things)
and three skills from heroes.

Now, how do we stack resistance?
1. If you do not have a spell resistance skill, you can either buy a Cloak or assemble a Hood and that's that. That's as high as it will ever go. Second Hoods and/or Cloaks will not offer additional bonuses to your resistance.

2. If you have a spell resistance skill, you may assemble the spell resistance item whenever you want. Previously (prior to 6.47), there was an issue with stacking spell resistance, but it is no longer an issue. So let me repeat that -- Item whenever you want, skill whenever you want.

Spell Resistance Stats from highest to lowest
===================================================
Heroes without spell resistance skills:

No Items: 25%
Cloak only: 36.25%
Hood only: 47.5%

===================================================
Anti-Mage:
Spell Shield level 4 gives 40% more spell resistance

No Items and skills: 25%
Cloak only: 36.25%
Hood only: 47.5%
Spell Shield only: 55%
Cloak and Spell Shield stacked: 61.75%
Hood and Spell Shield stacked: 68.5%
===================================================
Netherdrake:
Corrosive Skin level 4 gives 20% more spell resistance

No Items and skills: 25%
Cloak only: 36.25%
Corrosive Skin only: 40%
Hood only: 47.5%
Cloak and Corrosive Skin stacked: 49%
Hood and Corrosive Skin stacked: 58%

===================================================
Pudge:
Flesh Heap level 4 gives 16% more spell resistance

No Items and skills: 25%
Cloak only: 36.25%
Flesh Heap only: 37%
Cloak and Flesh Heap stacked: 46.45%
Hood only: 47.5%
Hood and Flesh Heap stacked: 55.9%
===================================================

Appendix A: Formula
How to calculate for the spell resistances:

A.) 2 Sources
This is for heroes without resistance skills or the 3 that do have it but do not choose to stack

Spell Resistance = (1 - (1 - S1) * (1 - S2)) * 100

The first source (S1) will always be your natural resistance of 0.25. The second source (S2) will be 0.15 for Cloak, 0.30 for Hood, 0.4 for Spell Shield, 0.2 for Netherdrake and 0.16 for Flesh Heap.

Example: Any hero with Hood

S1 = 0.25
S2 = 0.30
Spell Resistance = (1 - (1 - 0.25) * (1 - 0.30)) * 100
Spell Resistance = (1 - (0.75) * (0.70)) * 100
Spell Resistance = (1 - 0.525) * 100
Spell Resistance = 0.475 * 100
Spell Resistance = 47.5%

B.) 3 Sources
This is for Magina, Netherdrake and Pudge if they choose to stack an item with their resistance skill.

Spell Resistance = (1 - (1 - S1) * (1 - S2) * (1 - S3)) * 100

The first source (S1) will always be your natural resistance of 0.25. The second source (S2) will be 0.15 for Cloak or 0.30 for Hood. The third source (S3) will be 0.40 for Spell Shield, 0.20 for Corrosive Skin and 0.16 for Flesh Heap.

Example: Netherdrake with Cloak and Corrosive Skin

S1 = 0.25
S2 = 0.15
S3 = 0.20

Spell Resistance = (1 - (1 - 0.25) * (1 - 0.15) * (1 - 0.20)) * 100
Spell Resistance = (1 - (0.75) * (0.85) * (0.80)) * 100
Spell Resistance = (1 - (0.6375) * (0.80)) * 100
Spell Resistance = (1 - 0.51) * 100
Spell Resistance = 0.49 * 100
Spell Resistance = 49%