Calculating Hop Quantities

Hops are the flowers of the female hop plant, which is a perennial deciduous climbing vine.  They are the seasoning in beer, used to add bitterness to balance the sweetness of the malt and impart their aromas to the finished product.  Almost all hops available for sale in Australia are pelletised, made by crushing the hop flowers and forming them into pellets, although some varieties are now being released in cone or flower form.

The importance of hops in the beer cannot be overstated and it is essential to use fresh hops at all times.  We strongly recommend that you store all hops in the deep freeze.

There is a formula that can be used to calculate the quantity of hops required in a given recipe, based on the European Brewing Convention (EBC) Bitterness Units (BU).  We have a hop calculator here. Bitterness Units are expressed as milligrams of Alpha acid per litre of beer.  The Alpha acid content of all hops carried by any good home brew shop should be available at that shop.  As the Alpha acid content of any variety of hops will vary from crop to crop, we have not included a list with this leaflet.  Some typical Bitterness Unit figures for well known commercial beers are as follows:

 Victoria Bitter 26 BU
 Coopers Sparkling Ale 24 BU
 Guinness Stout  47 BU
 Bass Pale Ale 30 BU
 Lowenbrau 24 BU
 Pilsner Urquell 43 BU
 Cascade Premium Lager 25 BU

As you can see there is quite a bit of variance between different styles of beer.  This is very useful information as we are almost always trying to reproduce a particular commercial brand we like.  With this information and the final gravity of the beer, which determines the sweetness and body of the beer, we can reproduce the bitterness levels of our favourite beer.  The formula for this is as follows:
 

Formula to Caluculate the Quantity of Hops Required in a given Recepie
Weight in Grams = 10 x Required Bitterness Units x Batch Size
       Utilization Factor x Alpha Acid of Hops being used
 

To show this more clearly, see the example over the page for a 23 litre batch of Bass Pale Ale:

Example - Calculation of the quantity of Hops required for Bass Pale Ale
              (a)  (b) (c)
Required quantity of Hops in Grams = 10 x 30 x 25
              26.9 x 4.5
              (d)  (e)

             =  7500
              121.05

             =  61.95, say 60 grams of Goldings hops in the boil.

Now what do all these figures mean ?

(a)  This figure is there to ensure a result in whole numbers. ie; 61.95 instead of 6.195;

(b) The Bitterness units figure for Bass Pale Ale;

(c)  This is the batch size in litres at the end of the boil. ie 2 litres left in the boiler; 

(d) The utilisation factor, or the amount of Alpha acid that is actually used during a 45 minute boil.    The following table shows the percentage applicable for the boiling time for pellet and cone     hops:

 Boiling Time Pellet Hops Cone Hops 
    
 Less than 5 minutes  5.0% 4.2% 
 6 - 10 minutes 6.0%  5.0% 
 11 - 15 minutes 8.0% 6.7% 
 16 - 20 minutes 10.1% 8.4% 
 21 - 25 minutes 12.1% 10.1% 
 26 - 30 minutes 15.3% 12.7% 
 31 - 35 minutes 18.8% 15.7% 
 36 - 40 minutes 22.8% 19.0% 
 41 - 45 minutes 26.9% 22.4% 
 46 - 50 minutes 28.1% 23.4% 
 51 - 60 minutes 30.0% 25.0% 

(e) The alpha acid content of Goldings hops as a percentage by weight.
 

This formula is quite accurate when calculating hop quantities for normal strength beers.  When the Original Gravity of the wort to be boiled exceeds 1.050 an adjustment is required to the formula.  This is detailed over the page.

Gravity Adjustments
Where the gravity of the wort to be boiled exceeds 1.050 (for strong beers or when the boiler being used is too small to boil all of the wort), an adjustment to this formula is required.  The following formula may be used:
 

Gravity Adjustment = Gravity of Wort to be boiled - 1.050
             0.2
 

Formula to Caluculate the Quantity of Hops Required in a given Recepie with Gravity Adjustment

With the Gravity Adjustment, the new formula for calculating weight in grams of hops would then be:

Required quantity of Hops in Grams = (1 + Gravity Adjustment) x 10 x Required BU x Batch Size 
              Utilization Factor x Alpha Acid of Hops being used  
 
 

Calculation of the quantity of Hops required for Bass Pale Ale using the Gravity Adjustment formula.

If the wort being boiled for the previous recipe for a Bass Pale Ale had a Gravity of 1.090, the calculation would be as follows:

Gravity Adjustment = 1.090 - 1.050
               0.2
           = 0.2

Required quantity of Hops in Grams =  (1 + 0.2) x 10 x 30 x25
                    26.9 x 4.5

                 =  9000
                     121.05

                 = 74.35 grams, say 75 grams.