The item level for all items begin calculation the same way by taking the various stats on an item and multiplying them by their corresponding stat mods. Most stats have a stat mod of 1, including Strength, Agility, Intellect, Spirit, Resistances, and all rating stats. Stamina is the only â€œwhiteâ€ stat that has a stat mod of 2/3. The table below lists the various stats and their corresponding modifiers.
Mana per 5|5/2
The item value is determined by taking a stat multiplied by its modifier and raising it to the power of log(2)/log(1.5), which is approximately 1.7095, and adding it to the rest of the stats on the item each multiplied similarly. Once all stats are added up, the resulting value is raised to the 1/1.7095 power. The resulting equation is:
For most items this is the same item value that will go in to equation to determine the item level, but not all slots of equipment are created equal. When it comes to helms, chests, pants, and two handed weapons, their slot modifier is 1. Other slots have a different modifier.
Two Handed Weapon|1.00
One Handed Weapon|27/64
*When it comes to trinkets, Iâ€™m not sure of the exact slot modifier. Hyzenthleiâ€™s post listed them as a having a slot modifier of 17/25, but WoWWiki doesnâ€™t even list a slot modifier. I havenâ€™t done any testing to figure out the correct modifier as most trinkets have procs that are difficult to quantify in their budget.
Dividing the item value by the slot modifier yields the item slot value. This is the raw value that will go into equation to determine item level and weapon DPS. Depending on the quality of the gear and the suggested item level, one of many different formulas could be used. Originally in vanilla WoW, the formula to calculate the item level was a linear formula that had three different equations depending on the quality of the item.
Starting with item level 100 epics, however, the linear formula was replaced with a logarithmic formula that allowed greater scaling as item levels increased. Similarly, in Wrath of the Lich King, rare items and uncommon items from quest rewards shifted into using a logarithmic equation as well. As of patch 3.2, rare and uncommon items with random enchants now use the listed formulas below.
Sockets take up a flat amount of an items budget. It appears that to create a socket, Blizzard sacrifices 16 points from any stat they feel like choosing and then using that to create a socket of any color. The same stat can be sacrificed multiple times to create multiple sockets. The socket bonus seems to be just that, a bonus that consumes no portion of the itemâ€™s budget.
Like socket bonuses, theyâ€™re free and consume no portion of the itemâ€™s budget.
Weapon DPS is an interesting property of items as there seems to be multiple ways of calculating it. The recently introduced Heirloom items managed to answer and raise questions. Prior to level 57, making them equivalent to rare items from vanilla WoW, the Heirloom weapons do not scale linearly, but instead seem to alternate between linear and polynomial increases. From levels 58 to 67, the Heirloom weapons increase DPS exponentially as item level increases. From 68 to 80, the weapon DPS also increases exponentially, but at a different rate. Epic items from item level 100 to item level 226 all hold the same exponential scaling.
The equation for item level from item slot is a logarithmic equation and the equation from item level to weapon DPS would require an exponential equation, therefore an equation from item slot value, the value prior to item level, to weapon DPS would be a linear equation.
For rare items past item level 134, the following equation can determine one handed weapon DPS:
To calculate two handed weapon DPS, just multiply the result by 1.3, as a two handed weapon will have 30% more weapon DPS than a one handed weapon.
For epic items from item level 100 onward, the following equations determine weapon DPS:
One Handed Weapon:
Two Handed Weapon:
Ranged Weapons until item level 219:
The fact that epic items from TBC and WotLK share the same formula for weapon DPS leads me to believe that the formula for rare items in TBC may not be the same as the formula for rare items in WotLK.
A caveat about using the item slot value to calculate weapon DPS is that certain weapons, like , are under budget according to their item level and will display a lower weapon DPS than properly budgeted items at the same level.
For caster weapons the inherent DPS in a weapon is mostly useless. To overcome this problem, Blizzard began sacrificing some of the DPS on a weapon in order to allow it to be traded for Spell Power at a rate of 4 Spell Power to 1 Weapon DPS. From Molten Core to Sunwell, Blizzard had been sacrificing enough DPS to bring a one handed weapon down to approximately 41.4 DPS.
In WotLK sacrificing DPS works differently than previously. It appears that Blizzard is intending to make Spell Power intrinsic to a weapon in much the same way that weapons have a natural DPS. The calculation to determine a weapon's Spell Power is similar to the calculation for a weapon's DPS.
Rare Spell Power:
Epic Spell Power:
The only exception to this that Iâ€™ve found is the that has a higher than expected DPS. Unlike their melee counterparts, Heirloom items do not use the same Spell Power equation as rare quality items. They have a higher coefficient which explains their higher Spell Power compared to an equal item level rare.
With the exception of Thori'dal and the Tempest Keep legendaries, legendary items use the same calculation for stats and weapon DPS as an epic weapon of equivalent item level. Both Warglaives come out as being equivalent to being 156 epics and the stats on Val'anyr that appeared on the Armory put it at the equivalent as a 239 epic. What sets a legendary apart from an epic is the proc associated with it.
Items that have chance on hit mechanics or other special effects will have those counted towards the itemâ€™s budget. These fall under the same problem that trinkets have in that they are hard to quantify with a number and most likely have an assumed cost based on their theoretical benefit.