Extract to AG conversion IBU calculation?

I made the extract Falconer's Flight IPA from AHS last year. I just got BeerSmith 2 and did a conversion of that recipe to an AG recipe to see how the grain bill was estimated. The extract recipe I entered I to BeerSmith was pretty accurate as far as the ABV, which was right on or maybe off by .1%. I had previously calculated IBUs and calculated 67 which was right on BeerSmith's calculation. When I converted the recipe to AG, the ABV was still the same I believe, but the IBUs are calculated at about 95-97. What is causing this and how can I know that one of my created recipes would be correct?

I have no idea, but you might try inputting the recipe without using the conversion button. Basically the specialty malts stay the same and the base extract is replaced with base grain to equal the gravity points.

Can you post the recipe and mash profile?

Check your recipe's boil volume and batch volume in the all-grain recipe.

Is it possible the bitterness formula changed (Rager, Tinseth, Garetz)?

Also, double check that the hop names, AA%, quantities, and boil times remained the same. I doubt these changed, but it's worth making sure.

Here is what is in BeerSmith. I don't see any inconsistencies, but I've never done AG or created my own recipe.

Extract

BeerSmith 2 Recipe Printout - http://www.beersmith.com
Recipe: AHS Falconer's Flight
Brewer: Me
Asst Brewer:
Style: American IPA
TYPE: Extract
Taste: (30.0)

Recipe Specifications
--------------------------
Boil Size: 3.67 gal
Post Boil Volume: 3.38 gal
Batch Size (fermenter): 5.25 gal
Bottling Volume: 4.85 gal
Estimated OG: 1.065 SG
Estimated Color: 11.2 SRM
Estimated IBU: 65.1 IBUs
Brewhouse Efficiency: 72.00 %
Est Mash Efficiency: 0.0 %
Boil Time: 60 Minutes

Ingredients:
------------
Amt Name Type # %/IBU
1 lbs Caramel/Crystal Malt - 40L (40.0 SRM) Grain 1 9.3 %
8.0 oz Pale Malt (2 Row) US (2.0 SRM) Grain 2 4.7 %
4.0 oz Wheat, Torrified (1.7 SRM) Grain 3 2.3 %
1 lbs Extra Light Dry Extract (3.0 SRM) Dry Extract 4 9.3 %
8 lbs Pale Liquid Extract (8.0 SRM) Extract 5 74.4 %
2.00 oz Falconer's Flight [11.00 %] - Boil 60.0 Hop 6 45.6 IBUs
1.00 oz Falconer's Flight [11.00 %] - Boil 20.0 Hop 7 13.8 IBUs
0.50 oz Falconer's Flight [11.00 %] - Boil 15.0 Hop 8 5.7 IBUs
2.0 pkg Safale American (DCL/Fermentis #US-05) Yeast 9 -
1.50 oz Falconer's Flight [11.00 %] - Dry Hop 8. Hop 10 0.0 IBUs


Mash Schedule: Single Infusion, Light Body, No Mash Out
Total Grain Weight: 10 lbs 12.0 oz

All Grain

BeerSmith 2 Recipe Printout - http://www.beersmith.com
Recipe: AHS Falconer's Flight AG Conversion
Brewer: Me
Asst Brewer:
Style: American IPA
TYPE: All Grain
Taste: (30.0)

Recipe Specifications
--------------------------
Boil Size: 6.78 gal
Post Boil Volume: 6.24 gal
Batch Size (fermenter): 5.25 gal
Bottling Volume: 4.85 gal
Estimated OG: 1.063 SG
Estimated Color: 7.5 SRM
Estimated IBU: 93.9 IBUs
Brewhouse Efficiency: 72.00 %
Est Mash Efficiency: 82.3 %
Boil Time: 60 Minutes

Ingredients:
------------
Amt Name Type # %/IBU
11 lbs 8.0 oz Pale Malt (2 Row) US (2.0 SRM) Grain 1 90.2 %
1 lbs Caramel/Crystal Malt - 40L (40.0 SRM) Grain 2 7.8 %
4.0 oz Wheat, Torrified (1.7 SRM) Grain 3 2.0 %
2.00 oz Falconer's Flight [11.00 %] - Boil 60.0 Hop 4 65.8 IBUs
1.00 oz Falconer's Flight [11.00 %] - Boil 20.0 Hop 5 19.9 IBUs
0.50 oz Falconer's Flight [11.00 %] - Boil 15.0 Hop 6 8.2 IBUs
2.0 pkg Safale American (DCL/Fermentis #US-05) Yeast 7 -
1.50 oz Falconer's Flight [11.00 %] - Dry Hop 8. Hop 8 0.0 IBUs


Mash Schedule: Single Infusion, Medium Body, Batch Sparge
Total Grain Weight: 12 lbs 12.0 oz
----------------------------
Name Description Step Temperat Step Time
Mash In Add 15.94 qt of water at 163.7 F 152.0 F 60 min

Sparge: Batch sparge with 4 steps (Drain mash tun, , 1.53gal, 1.53gal, 1.53gal) of 168.0 F water

The difference is the boil size. You did a partial (concentrated) boil with the extract, and a full boil with the all grain.

khkman22 said:

When I converted the recipe to AG, the ABV was still the same I believe, but the IBUs are calculated at about 95-97. What is causing this and how can I know that one of my created recipes would be correct?

Click to expand...

Two main factors determine IBU extraction, OG and boil volume. In the case of extact vs all-grain of the same recipe both factors are at work. The all-grain is a full volume boil the extract is partial volume. A larger volume along with a more dilute solution (lower OG in the full volume) results in a higher IBU rate in the all-grain version. To get the same IBUs here you will need less hops in the full volume boil.

Thanks. I'm new at this so that's something I had probably read before, but I didn't really pay attention to since I have only bought kits to this point.