Hop age Calculator

The effects of age on hop alpha acids.

Homebrewers often leave ingredients lying around for a bit too long. Over time, as with almost everything, the alpha acid strength of hops diminishes. The rate of loss of strength is dependent on various factors:

  • HSI: hop storage index. This will depend on the hop. Choose one and it should be entered into the calculator.
  • Storage Temperature: the colder the hop storage temperature, the slower the rate of AA% decrease.
  • Storage Type: various options here, but it's all down to permeability and exposure to oxygen. The more oxygen that your hops are exposed to, the faster the AA% will decrease.

How to Use

  1. Click the Find Hop button

  1. Choose your hop - either scroll or search, then click the + button.
  2. Enter the actual AA% value if you have it - this will be on the packet somewhere.
  3. Enter the age of the hop in months
  4. Enter the storage temperature and storage type

Your calculated AA% will show in the greyed box.

I'd be a bit careful with this one as I've mentioned. I've heard anecdotal reports of folks assuming a bigger drop in AA% than expected and overbittering their beers. This could also be due to the bitterness contribution of other compounds that are less prone to the effects of ageing.

James Torr 18 Jun 22