Last days to enter the BrewHardware Giveaway!

Home Brew Forums > Home Brewing Beer > Extract Brewing > How do I calculate actual IBUs?
LinkBack Thread Tools
Old 12-08-2008, 01:52 AM   #1
Feedback Score: 0 reviews
Join Date: Sep 2008
Location: Lafayette, CO
Posts: 494
Liked 1 Times on 1 Posts

Default How do I calculate actual IBUs?

I do partial boil extract recipes and I'm trying to figure out how to make an IPA with a lot of hops. I've read a lot of the other threads on partial boils and maximum IBUs, and I have a good grasp on how high you can go.

I have been playing around with Beersmith, and the IBU calculator is obviously a bit odd. It lets you add hops and never stops increasing the IBUs. I got some good info from this thread:

but without going into a lot of math and averaging Tinseth estimation with other estimations, etc. etc., here's what I was thinking:

What about just adding hops to my Beersmith recipe until it shows 100 IBUs, and then do some easy math those IBUs with the 0 IBUs from the top off water.

For example: 3.5 gal boil with 100 IBUs, 1.5 gal top-off water (0 IBUs) would make a batch with 70 IBUs. (3.5*100 + 1.5*0)/5

Is this close enough, or am I missing something about Beersmith?


Kelpie Home Brewery, Lafayette Colorado
Primary: Creek Dog Stout x2, Two Dogs IPA, Grinning Kelpie Wheat
Secondary: empty :(
In Bottles: Belgian Wheat

Kungpaodog is offline
Reply With Quote Quick reply to this message
Old 12-08-2008, 03:02 AM   #2
Brew the brew!
Feedback Score: 13 reviews
nukebrewer's Avatar
Join Date: Oct 2008
Location: Groton, CT
Posts: 5,272
Liked 2774 Times on 1660 Posts
Likes Given: 5955


You've got it right. A somewhat simpler equation and the one I use is, (Vb/Vt)*IBU where Vb is boil volume, Vt is total batch volume and IBU is the IBUs BeerSmith calculates for you.


The only thing more asinine than stupid rules is the enforcement of rules simply because they are the rules.

Inhopsicated: A Beer Blog

Inhopsicated on Twitter

nukebrewer is offline
Reply With Quote Quick reply to this message
Old 12-09-2008, 02:33 AM   #3
Fat Guy Brewing
Feedback Score: 0 reviews
Join Date: Jun 2008
Location: Kansas City Metro
Posts: 215
Liked 1 Times on 1 Posts


If you want some extra math, try the calculation at the very bottom of this page. It might be a way to doublecheck BeerSmith.

Brewing Formulas

OOPS, sorry its not the bottom, its kind of in the middle. You'll see it, its a section titled IBU.


Owner, Brewer, Taster

Brewing: IPA
Fermenting: Oktoberfast
Drinking: Fat Guy Porter, Fat Guy Tire, AJ's Raspberry, SWMBO Slayer
Up Next: Xmas Ale

Fat Guy Brewing is offline
Reply With Quote Quick reply to this message

Quick Reply
Thread Tools

Similar Threads
Thread Thread Starter Forum Replies Last Post
Going to try actual chocolate Garyius Extract Brewing 22 12-05-2009 05:15 AM
Beersmith said OG: 1.049, Actual was 1.055 syd138 General Beer Discussion 4 04-06-2009 06:48 PM
How to calculate IBUs RiversC174 Beginners Beer Brewing Forum 7 02-12-2009 06:11 PM
Actual Website... Stevorino HomeBrewTalk Announcements & Feedback 11 02-24-2008 07:17 PM
Hop substitution - Do you calculate your IBUs? beergears Recipes/Ingredients 4 02-06-2008 01:29 AM

Newest Threads