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  1. #1

    IBU Tinseth formula

    Opening a can of worms:
    Some of you know I'm busy with bugubrew - which had me have a closer look at the formulas of calculating ibu's. There are several people with a different approach about what factors need to be considdered. The one I want to focus on in Tinseth - which seems to be a favourite to be referered to on the web when calculating ibu's.

    I found a webpage edited/created/verified by Glenn Tinseth with his formulas on it:
    More here:
    His simple calculator:

    OK my point is:
    I've added the formulas to bugubrew and calculates for the following for data:
    Batch size 45 litres, 1.051 OG, Hops: Centenial 9.5%AA 50g @ 60min ... and Bugubrew calculates 24.1 IBUs.
    From Glenn Tinseth calculator (link above) calculates 24 IBUs.
    Cool... Now !! calculates 27.7 IBUs for Tinseth
    BrewGr calculates 26.6 IBUs for Tinseth calculates 27.51 'Based on Tinseth's equations.'
    Application BrewMate calcs 25.74

    It seems they are all different for the same calculation theory (Tinseth) using the same brew data. Why's that? Are they all wrong? .. or am I missing something?
    I know IBUs is a 'relevant' number but what baffles me are the different results from different sources for the same formulas, making me doubt my own findings.

    Hoping to be enlightened.

  2. #2
    Senior Member JIGSAW's Avatar
    Join Date
    Jul 2013
    Cape Town
    Nai ek weeti

    Beersmith gives me closer to 27, so i'll use that

    The Problem With The World Is That Everyone Is A Few Drinks Behind.!

  3. #3
    Perhaps factoring in altitude? ie higher boil temp ?

  4. #4
    Senior Member
    Join Date
    Jan 2018
    Quote Originally Posted by CaPunT View Post
    Perhaps factoring in altitude? ie higher boil temp ?
    This. Check altitude and the hop utilization (sometimes called the hop utilization multiplier).

  5. #5
    That variance sounds like its in the range of the 'utilization factors' (cant remember the phrase they use) for the differences between pellets/ plugs/ fresh leaf hops? Is that something you have factored in at all?
    Based on Tinseth's equations. If you select pellets the utilization will increase by 10%.
    Maybe that and then maybe the controversial altitude factor mentioned above
    Last edited by Langchop; 11th November 2020 at 07:42. Reason: Man, you are going to be the most knowledgeable brewer after all this!
    "Dudddde...Hold my beer!".... ; "I wonder what will happen if I ...."

  6. #6
    Also, wort gravity affects the IBU achieved. I think most calculators take the average of the SG at the start of the boil and SG at end of the boil. Might be something to check in your calcs.

    IBU also obviously gets 'diluted' if you need to add water to correct the gravity into the fermenter
    "Dudddde...Hold my beer!".... ; "I wonder what will happen if I ...."

  7. #7
    Thanks for the feedback.
    I subsequently found that my calcs are for whole leaf and need to add 10% as Langchop pointed out from Brewersfriend .. but then 24.1 *1.1 = 26.4 .. is closer to the 'norm' yet still different from what other sites say.
    Tinseth does factor in OG in his 'Bigness factor' - thou he doesn't considder PBG but does includse constant factors that cater for this.
    I just checked on GF webapp and also calculates 27IBU - same as JIGSAW mentioned from BS.

    My point really is that for apparently one formula and the same data set there are several answers.

  8. #8

    Interesting read. Seems that BeerSmith was calculating the Tinseth formula incorrectly in 2010.
    Tinseth formula is for whole leaf hops.
    Need to add 10% to the value to get to Pellets, 8% for Plugs.
    It seems that modern day pellets, one needs to add 12% to the origional formulas.

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