Whirlpool Hop Utilisation %

[The Baron]

Hi anybody have a better or more accurate idea of whirlpool hop utilisation as I have just done a 70g hop addition at 90c for 30 minutes and it said 18.1 IBU's. The beer is now ready and on tasting it seems to be more bitter than 18 IBU's to me, don't get me wrong I erred on the low side so as that if it came out higher it would not be too bitter for my taste as I don not like bitter too much. I also realise that IBU's do not always give a true perception of what bitterness will be in each beer and should be used as a guide.
Ps on Brewers friend it gave 3.9% at 90c for 30 mins

 

[peebee]

In what OG of beer?

18 IBU in plain water would make anyone wish they hadn't put it in their mouth. I do find the BU:GU ratio to be not that bad (compared to IBU alone) at pre-judging perception of bitterness.

 

[The Baron]

Hi Peebee it was 1.038 OG and finished at 1,008 so approx 3.9ABV the BU/GU ratio is 0.48. All I am trying to do is find out if the % they quote are near the mark or not, the hops were Anthanum El Dorado and Cascade at 40g, 40g and 30g respectively so 110g in total and not the typo of 70g

 

[peebee]

The other thing I do to try and get consistent bittering is estimate the remaining IBUs in hops stored in the various ways: Once I have them they go in the freezer, either packed in the original metalized sealed packs or as opened packs.

Beersmith does my calculating, but there are other calculators. Particularly important if using American "C" hops (Cascades have a "hop storage index" of 50% alpha acid lost per 6 months).