Converting Hops in All-Grain to Extract Recipe

Question

I have this All-Grain recipe that I'm converting to Extract. Do you basically just increase the hops until the IBUs match the original measurement? I've gotten the OG fairly close and the SRM is a little darker, which I'm expecting from extract. I increased the boil hops and the IBU is only off by 8. Anyone have any suggestions?

Here is the original recipe:

Boil Size: 7.11
Boil Time: 60 min
Taste Rating(out of 50): 42.0
Brewhouse Efficiency: 70.00
Mash Temperature: 150 F
Mash Time: 60 Minutes

Efficency was calculated @ 70% Brewhouse
Est Original Gravity: 1.098 SG
Est Final Gravity: 1.021
Estimated Alcohol by Vol: 10.05 %
Bitterness: 138.2 IBU
Calories: 458 cal/pint
Est Color: 8.8 SRM

14.50 lb Pale Malt (2 Row) US (2.0 SRM) Grain 70.73 %
3.00 lb Vienna Malt (3.5 SRM) Grain 14.63 %
1.00 lb Caramel/Crystal Malt - 20L (20.0 SRM) Grain 4.88 %
0.50 lb Cara-Pils/Dextrine (2.0 SRM) Grain 2.44 %
0.50 lb Honey Malt (25.0 SRM) Grain 2.44 %

1.25 oz Columbus (Tomahawk) [15.20 %] (60 min) (First Wort Hop) Hops 45.3IBU
1.00 oz Simcoe [12.70 %] (60 min) Hops 27.5 IBU
1.00 oz Chinook [12.40 %] (45 min) Hops 24.7 IBU
1.00 oz Centennial [11.50 %] (30 min) Hops 19.1 IBU
1.00 oz Citra [11.00 %] (15 min) Hops 11.8 IBU
1.00 oz Amarillo Gold [9.40 %] (10 min) Hops 7.4 IBU
2.00 oz Amarillo Gold [9.40 %] (0 min) (Aroma Hop-Steep) Hops
2.00 oz Simcoe [12.70 %] (0 min) (Aroma Hop-Steep) Hops
3.00 oz Simcoe [12.70 %] (Dry Hop 7 days) Hops 
1.00 tab Whirlfloc (Boil 15.0 min) Misc
1.10 tsp Yeast Nutrient (Boil 10.0 min) Misc
1.40 lb Honey (0.0 SRM) Sugar 4.88% (Boil 10.0 min)

And here is my converted recipe for extract:

Est Original Gravity: 1.089 SG
Est Final Gravity: 1.019
Estimated Alcohol by Vol: 9.4 %
Bitterness: 130.3 IBU
Est Color: 9.6 SRM

11 lbs Briess Golden Light Liquid Extract
3 lbs Weyermann Vienna Malts
1 lb Briess 2 Row Caramel 20L Malt
.5 lb Briess Organic Cara-Pils
.5 lb Gambrinus Honey Malt

2 oz Columbus (Tomahawk) [15.20 %] (60 min) (First Wort Hop) Hops
2 oz Simcoe [12.70 %] (60 min) Hops
1.5 oz Chinook [12.40 %] (45 min) Hops 
1.5 oz Centennial [11.50 %] (30 min) Hops 
1.5 oz Citra [11.00 %] (15 min) Hops 
1.5 oz Amarillo Gold [9.40 %] (10 min) Hops 
2.00 oz Amarillo Gold [9.40 %] (0 min) (Aroma Hop-Steep) Hops 
2.00 oz Simcoe [12.70 %] (0 min) (Aroma Hop-Steep) Hops 
3.00 oz Simcoe [12.70 %] (Dry Hop 12 days) Hops 
1 oz Amarillo Gold [9.40 %] (Dry Hop 12 days) Hops 
1.40 lb Honey (0.0 SRM) Sugar 4.88% (Boil 10.0 min)

Answer 1

It's not the extract specifically that's the problem but the lower utilization resulting from the higher gravity of a partial boil. If you're not doing a partial boil, then no need to scale. But if you are, then your main recourse is to scale the bittering hops to match the target IBUs, as you've done.

Scaling the FWH addition is interesting, since as well as increased bitterness, you get some aroma contribution, but the difference if any will be subtle. More pertinent, how long will you be steeping the FW hops. FWH are typically steeped for 60-90 mins or more in a all grain brew, or longer - however long it takes to drain the mash, perform the sparge and then bring to a boil. It's this long exposure to warm wort that gives the higher utilization for FWH - sources cite a 10 percent increase. When doing a short steep, such as the time it takes to boil the water for the partial boil, I wouldn't count too much on the additional utilization from FWH and simply register these as regular boil hops unless you plan to steep them for the time indicated.

But I should say that this just splitting hairs and mostly academic - in practice a 5 IBU difference is not so apparent, imperceptible to some, and even more so with the high hopping rates here.

• First Wort Hopping, Beersmith brew blog