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Scoring Charms

May 25, 2022




May 25, 2022

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Charms are a unique beast that does not fit in to the same calculation scheme I've used for rare items. This article outlines the calculations used to assign a score for charms.

Use Cases

Although use cases (caster/melee, PvP/PvM) are helpful for valuing rare items, I just don't think charms have enough variation for use cases to help more than they hurt. Thus, charm calculations do not account for any specific use case.

Normalizing Size

To compare charms of different sizes (small/large/grand) we must first normalize by dividing by the number of slots used. Thus, if a large charm rolls 10 life, it will be calculated as if it is a small charm that rolled 5 life.

However for grand charms which have +1 to a specific skill tree, the max possible values for grand charms will be used, rather than normalizing to the small charm value. Ie: +45 life on a grand charm will be a perfect roll, rather than treating it like 15 life on a small charm.


To fairly value rolls, mods are compared only against the same affix. Suffixes vs suffixes, and prefixes vs prefixes.

Read the full list of charm weights

Combining Mods

The tricky part about scoring charms is combining mods. How to get 1 score to capture to effect of both the prefix and the affix?

I considered multiple strategies: simple addition, multiplication, some trained polynomial function... But ultimately, I decided on taking the magnitude.

Score = sqrt( prefix^2 + suffix^2 )

With a max score for either a prefix or suffix set to 10, then the max score for a perfect combination of both prefix and suffix is sqrt(200) ~= 14.14

Using this scoring method, we can visualize the score with something like this:

Score Examples


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Comments :
Blongz82 May 10, 2023

Thank you from all the noobs in the d2r world your website has given people like me and all other noobs out there to not get ripped off by sharks who swarm the waters during a new ladder season

DV2TR Jun 11, 2022

Awesome addition, as usual: Thanks for your effort! :) For large charms there seems to be a wrong cap for the steel prefix. It's capped at 77 here but I just found one with 107.

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