I'm trying to figure out how thorns works so I can start deciding how to approach making a viable thorns build. Stacking some thorns on my Crusader has led me to believe that it's not as simple as it sounded at first.

I have around 7,000 thorns right now, but when enemies attack me, they take over 90,000 damage. I've also seen the thorns damage crit, and I've also seen enemies take upwards of 2 million damage from a single activation of thorns.

With Vo'Toyias Spiker equipped and using Iron Skin with Reflective Skin and Provoke with Charged Up, I've just utterly melted enemies, seeing crits of over 8 million. None of my active attacks can deal even 2 million damage, so these massive numbers must be from some combination of these skills.

Is thorns return damage somehow a function of how much damage I sustain? What if I block or dodge? What is the approximate formula for damage return based on my current thorns?

  • I don't see why it wouldn't scale with either damage dealt or damage inflicted. I also expect it's different for melee vs. missile vs. non-physical.
    – MBraedley
    Commented Mar 27, 2014 at 11:11
  • IIRC I've read somewhere that block/dodge still results in a thorns hit.
    – Arperum
    Commented Mar 27, 2014 at 12:21
  • My guess is that the thorns damage is affected by your damage multiplier from your primary attribute. I also think it would probably be affected by the +x% to physical damage mod on items. Both of these theories are untested, but I also noticed my thorns hitting for a lot more than the amount stated on char. screen Commented Mar 27, 2014 at 13:35
  • @DiabloMonkey what about the damage multiplier from cc/cd? Either way that makes thorns much more interesting.
    – l I
    Commented Mar 27, 2014 at 13:43
  • @z- My crusdaer is not quite up to 70 and I noticed it doing decent damage (2 mil crits) and I was not stacking thorns on gear intentionally either. I think it could be a fun option to try out. Commented Mar 27, 2014 at 14:01

6 Answers 6


After doing some math, I arrived at the following formulas for thorns damage:

Regular Attack

  • ((S / 100 / 4) + 1) * T

Reflective Skin Attack

  • ((S / 100) + 1) * 2T * (P / 100 + 1)


  • S is Strength (or mainstat)
  • T is your thorns damage
  • P is your Physical Damage bonus (as a percent)

It does not appear that regular thorns damage can crit, nor is it based off your weapon damage or the damage done to you. It did not to appear to be affected by any damage reduction modifiers nor is it improved by bonuses to Physical Damage Skills. It is scaled according to your mainstat by 1/4

Reflective Skin does indeed double your base thorns damage. However, because it is a skill doing the damage and not the thorns mechanic, it scales off your mainstat like all other skills (not at a 1/4 ratio). It is also then eligible to crit and receive your "+X% Damage to Physical Skills" bonuses. This is the reason for the (more than 2x) large spike in damage when using Reflective Skin.

An example:

For a crusader with 5000 Strength and 10000 Thorns and 20% Bonus to Physical Skills:

  • A regular attack would deal 135,000 damage.
  • An attack while Reflective Skin is active would deal 1,224,000 damage (with the option to crit).

After doing some research, I have reached a few conclusions, plus found how the approximate damage works.

Thorns return damage does not depend on how much damage the attack against you does. It's calculated by your base thorns times a multiplier based on your primary stat. The multiplier is one quarter of the bonus provided to your attacking damage. For example, if you have 20,000 thorns, and 6,000 strength, then you'll get 1500% bonus thorns damage (6000 / 4 as a percentage), which amounts to 320,000 thorns damage to enemies when they attack you (20,000 base plus 300,000 bonus from primary stat). This can then crit based on your normal crit chance and crit damage.

All of the insanely high damage numbers occur using the Iron Skin skill with the Reflective Skin rune, which appears to be bugged currently and do lots of wonky stuff (including killing allied Crusaders).

  • Re killing crusaders in that linked post, IIRC, one law has a perk where you take damage on your allies' behalf. (Justice > Protect Innocent) Possibly unrelated to Iron Skin? ( diablofans.com/blizz-tracker/topic/… )
    – horatio
    Commented Mar 28, 2014 at 18:08
  • I can see throns only crit when i use Iron Skin. Without it i don't see crits with throns.
    – user73072
    Commented Mar 29, 2014 at 17:13
  • So, weapon damage does not directly affect your thorns damage?
    – prolink007
    Commented Apr 1, 2014 at 18:18

I did some testing because I was wondering the same question and came to the conclusion that only your main stat and dmg taken debuffs on the target affect thorns damage (dmg buffs on yourself do not increase thorns dmg, atleast not the ones I tested with), dmg taken debuff affects thorns dmg by 75% the normal amount and main stat increases thorns dmg about 25% of the normal dmg increase.


In the 2.0.5 patch notes, they mention changing the item Sanguinary Vambraces. Inside this change they mention the modifier.

The Thorns damage dealt by these bracers will now benefit from your main stat damage increase at a 25% rate, as normal Thorns damage does

Therefore, it is modified by 25% of your primary attribute. Confirmed.

  • I can confirm that the damage has been boosted, but I have no idea what the formula is. I have 8458 strength and 31,959 thorns which gives me exactly 707,732 thorns damage every hit. It never crits and is never random. When these bracers procs, it always does 5,748,620 and also never crits and never random. Thorns damage is (str/400+1)*thorns (25% bonus from Strength), but how is Sanguinary Vambraces damage calculated?
    – James
    Commented May 28, 2014 at 7:39
  • If I change to 7495 strength, 27,429 thorns, then bracer damage is 4,229,549. If I change to 8458 strength but 23,306 thorns, then bracers is like 3,834,577. (It's hard to read the bracer damage since they appear in conjunction with the normal thorns damage.)
    – James
    Commented May 28, 2014 at 8:23

Here's a thorns crusader damage calculator: http://www.ring.lt/crusader/

  • 1
    Could you give a formula for your calculator? How does physical damage affect it?
    – user79448
    Commented Jun 11, 2014 at 8:09

I have analyzed the source code of the crusader thorns DPS calculator mentioned in user77988's answer. The important lines are

var damage = Math.round(((parseInt(strength)/400)+1)*parseInt(thorns));
var rsdamage = Math.round(((parseInt(strength)/100)+1)*2*parseInt(thorns)*(phy/100+1));

Where damage is regular Thorns damage, rsdamage is Reflective Skin Damage. Converting from Javascript to regular Math, that is

D  = (S/400+1)*T
RS = (S/100+1)*2*T*(P/100+1)

where S is strength, T is thorns and P is the bonus damage to physical skills in %

This is identical to the formulas in TheCheeseGod's answer.

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