Testing spell power coefficients First , you need to understand that a great number of casts is not needed . We are not doing statistics , we are using the games mechanisms to analyse spell damage more efficiently . In order to test the coefficient of a spell , we need to look at the range of damage the spell can do without any spell power . The best way to do this is to go to a database site , find the relevant rank of the spell , and look at the tooltip . Then , in order to test efficiently , make sure there are no buffs that will soon run out . Make sure the amount of bonus spell damage will remain static . Take away any items which may proc bonus damage effects . Also , you will need to either remove all your talents , or to account for them in your calculations , but be careful , as this can be quite tricky . The most important thing to know about spell damage is that it increases your spell ' s damage by a flat value . It does not act randomly at all . The range of damage which you can deal is equal to the range of damage you would deal without . Let me illustrate : Imagine you have a spell which is lucky enough to use 100 % of spell power . Say that spell , according to the tooltip , deals between 600 and 700 damage . A range of 100 damage . So if you have 150 bonus damage , the spell will always deal between 750 and 850 damage , the same range . So essentially , we will be researching the range rather than an average . If we were researching the coefficient for this spell , with a tooltip of 600 - 700 and a 150 bonus spell damage , we would cast the spell a high number of times with hopes of getting a highest and lowest value with a range of 100 . Once you do get that range , you can easily calculate the way in which bonus damage is applied . You can look , for example , at the highest value each time . Without spell power , it would be 700 . With spell power , it is 850 . The difference is 150 damage . That is exacly 100 % of your spell power . Rounding . The damage your attack does will always be an integer . However your spell coefficient times your spellpower may not be an integer ( even more so after you include talents that increase all damage by 3 % ) . What WoW does is compute the spell damage using floating point math , and then round either up or down ( probably based on a random number generator ) to one of the nearby integers . For a really precise spell coefficient , you will want to account for this . Suppose you have a spell with a damage range from 445 to 488 . You cast the spell several times with 901 spell damage and your lowest and highest ( non - crit , non - partial - resist ) damage values are 952 and 976 . You know know that 445 + 901 * " coefficient " is at most 952 . 999 . If the coefficient were any larger , you could have never seen a cast that did only 952 damage . Your 952 might have been from a base damage of 445 , and in floating point might have really been 952 . 999 . We can use this to compute an upper bound on the spell coefficient : The spell coefficient is no more than ( 952 + 1 - 445 ) / 901 = 56 . 38 % . If the spell coefficient were any higher , the spell would have always done at least 953 damage . Use a similar formula ( against the max damage numbers ) to compute a lower bound on the coefficient : ( 976 - 1 - 488 ) / 901 = 54 . 05 % . If the spell coefficient was any lower , every cast would have done at most 975 damage . At this point you know the spell coefficient is between 54 . 05 % and 56 . 38 % . To get a tigher range you ' ll need to run more tests . And that ' s how you do it . If you give it a little thought you won ' t need to untalent , and you can even use crits in your analysis , but be careful !