Item utility is the sum of the value of each bonus on an item times a multiplier assigned to that bonus type.
The utility multipliers for each bonus type are found in this table.

Id	Bonus Name	Utility Multiplier
1	Stats	0.6666667
2	Skills	5.0
4	Hit Points	0.25
5	Resistance	2.0
8	Toa Melee Damage	5.0
9	Toa Magic Damage	5.0
10	Toa Style Damage	5.0
11	Toa Archery Range	5.0
12	Toa Spell Range	5.0
13	Toa Spell Duration	2.0
14	Toa Buff Bonus	2.0
15	Toa Debuff Bonus	2.0
16	Toa Heal Bonus	2.0
17	Toa Fatigue	2.0
19	Toa Melee Speed	5.0
20	Toa Archery Speed	5.0
21	Toa Cast Speed	5.0
22	Armor Factor (AF)	1.0
27	Toa Archery Damage	5.0
28	Toa Overcap	2.0
29	Toa Hit Points Cap	0.25
30	Toa Power Pool Cap	2.0
31	Toa Fatigue Cap	2.0
32	Toa Resistance Piercing	5.0
34	Toa Power Pool	2.0
35	Toa Artifact	5.0
37	Spell Power Cost Reduction (PvE)	2.0
64	Mythical Cap Increase	2.0
68	Mythical Resist and Cap	4.0
75	Mythical Stat and Cap Increase	4.0

Note: Zero-utility bonuses are excluded.