Beersmith

How do you calculate you IBUs in your recipes?

For example: Your "pig-n-a-poke-pale-ale" you have

50.8 IBUs for the 2.00 oz Centennial (10.3%) 45min.

I am using "The New Complete Joy of Homebrewing" 2nd edition. pgs 265-268.

If I use the formula on pg267 and chart on pg 268. I get an IBU of 76.86. I am using the chart and determined you have 1.75 lbs of extract per gallon assuming you are boiling 3.98 gallons as the recipe states this gives you roughly 25% utilization on a 45 minute boil.

If you go back to page 267 and put the numbers in the formula : 2.00 oz times10.3 %AAtimes25% utilization

divided by 6.7 (for 5 gallons total) = 76.86.

Am I doing anything wrong or are you using some other

way to calculate the IBUs. I have been calculating IBUs for some recipes I have put together but am worried about the big difference I am seeing in recipes.

I just wander ??