Using the Hop Utilization & IBU Graphs

by Bob Jones

These graphs were handed out at the September meeting for Tinseth’s IBU calculations. Contact Bob if you would like a larger or electronic copy.

Look along the Boil Time X axis and located the amount of time the hop will be boiled. Look up the graph and locate your Wort Gravity. Project this point over to the Y axis to obtain the AA Utilization for the hop.

Now take the AA Utilization obtained in step 1 and find that value along the X axis of the appropriate IBUs in Wort Graph (5 or 10 gallon). Look up the graph, locating the Hop %AA for the hop. Project this point over to the Y axis to finally obtain the IBU for the individual hop.

Note:

These graphs will locate the IBU for 1 ounce of hop with a given %AA in either a 5 gallon or 10 gallon batch size.

Example:

How many IBUs will 2 ounces of 5%AA hop contribute to 5 gallons of 1.060 wort if boiled 60 minutes?

From the Hop AA Utilization graph we look at the X axis and find the 60 minute boil time. Looking up the graph we locate the intersection of 1.060. We then project over to the Y axis and find the utilization of 21.1%.

On the second graph we now locate the Utilization of 21.1% on the X axis and project this up to the Hop %AA of 5%. Then we project over to the Y axis and find the IBU contributed to the wort of 16.

The above 16 was for 1 ounce of hop so we multiply that by 2 to get: 2 x 16 = 32 IBUs.

You must do this for each hop added to the boil and add them all up to obtain the total IBUs in the wort.

Notes:

Make sure you use the correct graph for a 5 or 10 gallon batch size.

These graphs utilize a fudge factor of 4.15 as suggested by Glen Tinseth. If you want to tune the IBU calculations to your personal brewery, then you should go straight to the mathematical formulas.