Basic guide to how MF works.
This is a fairly simple guide to try to clarify some of the confusion surrounding MF% ages and what they do. If you read nothing else here, read points 4 and 5 in the summary at the end.

What does Magic Find do?
Magic find increases the chances of a dropped item being of a higher magical quality.

What does Magic Find NOT do?
Magic find has no effect on the base item that drops, nor does it have any effect on whether the item is superior, normal, inferior, socketed if a white / grey item is selected, or Etheral. Because MF has no effect on the base item selection process it also has no effect on rune finding.

The Basic drop mechanics
When an item is dropped in D2 it goes through a multi staged selection process before it is actually generated. I will not go through the mechanics of the base item drops here. We are only concerned with what happens to the item after it has been selected that one will drop. It is however relevant to Magic Finding that the only way to increase the chance of an item being generated when a monster is killed is by having more players in the game.

The item quality selection process
We know an item has been selected to drop.

The game now has to decide what magical properties the item will have, if any, and so it goes through the following selection process which is done in turn for each item assuming it is relevant (clearly not applicable to runes, potions, gold etc).

1) Roll to check if it is Unique item (Gold). If this fails* then
2) Roll to check if it is a Set item (Green). If this fails* then
3) Roll to check if it is a Rare item (Yellow). If this fails then
4) Roll to check if it is a Magic item (Blue). If this fails then
5) Generate a White item with some of the following properties: Superior/Normal/Inferior/Sockets.
6) All items will finally go through a check to see if it is Etheral. Note that items which are indestructible cannot also spawn ethereal unless they specifically always spawn ethereal as is the case for certain uniques.
7) Drop the final outcome.

*There are times when this check will pass, but there may not be a unique or set item available. Instead of carrying on to the next check the game generates a ‘failed unique’ or a ‘failed set’ item. This results in a triple durability rare item for failed uniques and a double durability magic item for failed sets.

The order of this selection process is vital. I will come back to that in the summary.

So, how does Magic Find work?
Items always have a chance of passing any the check rolls above.

However, Magic Find increases the chance of making each of the quality checks in turn.

Magic find increases the base chance of making the quality check by the Effective Magic Find percentage for each quality. The effective MF percentages for each item quality are:

Effective MF for Unique items (Gold) = (MF*250)/(MF+250)
Effective MF for Set items (Green) = (MF*500)/(MF+500)
Effective MF for Rare items (Yellow) = (MF*600)/(MF+600)
Effective MF for Magic items (Blue) = MF

This means that the relationship is not linear, and if you fancy sticking the above into Excel and make a graph you’ll see just how non linear the relationship is. Here is a small table to give you the idea:

-------Effective MF %
MF%---Unique---Set-----Rare-----Magic
--10---- 9.62---- 9.80---- 9.84-----10.00
-100-- 71.43--- 83.33--- 85.71-- 100.00
-200-- 111.11- 142.86- 187.50-- 200.00
-300-- 136.36- 187.50- 200.00-- 300.00
-500-- 166.67- 250.00- 272.73-- 500.00
1000- 200.00-- 333.33- 375.00- 1000.00
Unlimited-250.00-500.00-600.00-Unlimited

This is the famous diminishing returns curve that is so often mentioned where the higher your MF % the more you have to add to achieve any marked improvement for Uniques in particular.

Summary
1. You do not need any added MF to find Uniques. There is always a chance.
2. Added MF increases your chances of upgrading the items that drop.
3. For uniques in particular we can see that the amount of help we can get from MF is restricted (severely), so killing things quickly becomes more important than adding more MF%. For example going from 500-1000 you gain comparatively little in terms of effective MF for generating uniques, but you will probably ruin any chance of killing things quickly if at all in Hell.
4. Because of the order the game checks for quality of items, more MF always gives a higher chance of rolling unique items.
5. Because of the order the game checks for quality of items, the only things that actually go down as MF goes up are White / Gray items.
6. When hunting socketables reduce your MF.

I will not claim to be the originator of any of this information. It is merely a simplified summary of the various guides and discussions I have read. In particular GTAMaloy]’s “Guide to all that is items" is a very worthwhile read hosted at Baron's Bazar, B-net, The Amazon Basin etc.

This post was edited by AyeCaramba on Jun 1 2007 08:43am

I just hope people can read & understand what is posted here.

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For those who want a step by step walk through of how an item is actually generated, check out my guide in my signature as this will detail how a specific base item is selected and then how the above magic find table is applied to determine if the dropped item turns out gold, green, yellow, or blue.

nice guide thanks

Nice job.

nice

nice, concise theory. well covered. i will use on my new Mf charc...

Yea, good guide. Hope it'll stop all the "how many MF do I need" threads that keep popping up in dozens a day.

Btw, I have some questions regarding jewelry and charms:

Since they have no whites, does MF increase the chance of finding amulets and charms?

I sincerely hope it will stop the threads too.

Even though Charms and Amulets (Rings and Jewels too for that matter) are always at least magical (blue), they are still base items, and as such the MF will not make it more likely for one to be selected during the base item selection process. Some monsters have a greater likelyhood of dropping some of these, but that is by the by.

MF then works in the normal way when selection the quality of your Charm, amulet, ring or jewel in exactly the same way as anything else except you stop at magic if all the others fail. (For charms the only roll will be for Unique GC, all other charms will simply just spawn blue).

Hope it helps.

Interesting

Might go do some mfing

really helpful, just hope that many ppl read it =)