I'm over here using the real ibu formula like... Huh?!?!..

W=

B ∗ V 1000 ∗ A ∗ U

Where W is the total weight of the hops to be used in grams, B is the desired

bitterness in IBUs, V is the final volume of post boil wort in the kettle in liters,

A is the alpha acid content of the hops (4.7% AA means that A = 0.047), and

U is the assumed hop utilization.

For example targeting 16 IBUs and assuming a utilization of 28% (i.e.

set U = 0.28 and B = 16). Utilization will vary from system to system; if your

beer ends up too bitter, try raising the utilization to 30%, and if it ends up

not bitter enough try lowering it to 25%. For example, assuming your post boil

volume is 21 liters, your hops contain 4% alpha acids, and your utilization is

28%, you would use a total of 30 grams of hops.