Alpha numbers on hops package don't match recipe editor

[SabreSteve]

Hey all! It's brewday here! It'll be an interesting one because I'm trying to line it up so the bulk of my brew session falls during my son's nap time. Nothing could possibly go wrong there. So noticed something this morning as I was gathering up my ingredients. My challenger hops say on the package that the alpha% is 5.3 but I was pretty sure the listing in the recipe editor was 8.5. so I double checked. I then manually changed the AA in the recipe to 5.3 which of course made the IBUs go down significantly. Fortunately I had accidentally bought an extra 1 ounce package of hops (call it a lucky mistake) that I figured I'd just have to incorporate into my next batch. So I was able to increase the amount of hops in the recipe to get the IBUs relatively close to where they were before. My main question is if this is pretty common? Do the same variety of hops often vary so much in how much acids they contain? I'm opting to trust the grower but can where it's grown make that much difference. My LHBS seems to primarily carry Yakima Chief hops, do their hops often differ from the bulk of those same varieties. I'm only asking because it seems to me that it could significantly impact the characteristics of the finished beer if you aren't paying attention. Should I be more vigilant about this going forward?

 

[Nosybear]

Hops can vary immensely in the amount of AA. Adding to the confusion, AA decreases as the hops age. You did the right thing by changing the AA in the recipe, then correcting. You can do the same thing using proportions: AA1/AA2=Wt1/Wt2 (AA is alpha acid, Wt is weight). Remember this: IBUs at our level are a SWAG (Scientific wild-a**ed guess) at best. Without a bunch of analytic equipment most of us can't afford, you're having to rely on someone, might as well be the grower, at least until you can make the predictions using experience. Hops are agricultural products, variation is normal, not only from batch to batch but within batches. Nothing to obsess over but something to be aware of.

 

[Craigerrr]

Even after 40+ brews, I struggle to make every batch of beer "X" exactly the same every single time.
As long as the AA's are close, I don't bother with it too much.
What you had there was quite a spread, so good catch, and good adjustment on the fly!

 

[J A]

My challenger hops say on the package that the alpha% is 5.3 but I was pretty sure the listing in the recipe editor was 8.5. so I double checked. I then manually changed the AA in the recipe to 5.3 which of course made the IBUs go down significantly

You have to do that with every batch of hops you buy. They're never the same.
Make the AA number in the calculator match what you're using and then vary the amount to get the IBUs you want.