Fermentation Science, Brewing & Recipe Formulation
Tinseth Hop Utilization & IBU Bitterness Formula
Calculate Kettle Added Alpha Acids (mg/L), Glenn Tinseth’s Wort-Gravity & Boil-Time Utilization 1.65*(0.000125^(SG - 1))*((1 - EXP(-0.04*t))/4.15), International Bitterness Units (IBU), and BU:GU Balance Ratio.
Account for both high-gravity wort suppression and exponential iso-alpha isomerization!
During kettle boiling, insoluble hop humulones (alpha acids) thermally isomerize into bitter iso-alpha acids (1 IBU = 1 mg/L dissolved iso-alpha acids). Flat utilization lookup tables fail when scaling recipes to Imperial IPAs or concentrated partial boils because dissolved malt sugars suppress alpha-acid solubility exponentially! Glenn Tinseth’s industry-standard 1997 empirical equation separates utilization into two coupled physical factors: Bigness_Factor = 1.65 * (0.000125 ^ (Boil_SG - 1)) and Boil_Time_Factor = (1 - EXP(-0.04 * Boil_Min)) / 4.15, giving Decimal_Utilization = Bigness_Factor * Boil_Time_Factor and Finished Bitterness IBU = ((Hop_Mass_g * Alpha_Frac * 1000) / Post_Boil_Wort_L) * Decimal_Utilization!
Verify on a 20-liter West Coast IPA batch—Kettle_Boil_SG = 1.050 (B2 -> Gravity Units GU = 50), Boil_Time = 60 min (B3), Pellet_Hop_Addition = 50 g (B4), Hop_Alpha_Acid_Fraction = 0.10 (10.0% AA, B5), and Post_Boil_Volume = 20 L (B6): Added Alpha-Acid Concentration is (50 * 0.10 * 1000) / 20 = 250.00 mg/L (E2); Tinseth Utilization is 1.65 * (0.000125^0.05) * ((1 - EXP(-2.4)) / 4.15) = 0.2307 (23.07% in E3); Finished Bitterness is 250 * 0.23067 = 57.67 IBU (E4); and Ray Daniels’ Bitterness-to-Gravity Ratio BU:GU is 57.67 / 50 = 1.15 (E5)!
| Tinseth Kettle Hop Metric (SG=1.050, t=60m, 50g @ 10% AA, 20L Wort) | Formula | Verified Output |
|---|---|---|
| Added Alpha Acids (mg/L) | (Hop_g * Alpha_Frac * 1000) / Wort_L | 250.00 mg/L |
| Tinseth Decimal Utilization | 1.65*(0.000125^(SG-1))*((1-EXP(-0.04*t))/4.15) | 0.2307 (23.07%; 0.0000 @ t=0) |
| International Bitterness (IBU) | Added_Alpha_mg_L * Utilization | 57.67 IBU (0.00 IBU @ t=0) |
| Bitterness Ratio (BU : GU) | IBU / ((SG - 1) * 1000) | 1.15 BU:GU |
Glenn Tinseth International Bitterness Units (IBU) Formula
Validate Boil_SG > 1.000 (up to 1.200), Boil_Time >= 0, Hop_Mass > 0, 0 < Alpha_Frac < 1, and Wort_Volume > 0!
=LET(sg_w, B2, t_mn, B3, hp_g, B4, aa_f, B5, vl_l, B6, IF(OR(sg_w <= 1, sg_w > 1.2, t_mn < 0, hp_g <= 0, aa_f <= 0, aa_f >= 1, vl_l <= 0), "Invalid Kettle Hop Schedule", LET(ad_a, (hp_g * aa_f * 1000) / vl_l, bg_f, 1.65 * (0.000125 ^ (sg_w - 1)), tm_f, (1 - EXP(-0.04 * t_mn)) / 4.15, ROUND(ad_a * bg_f * tm_f, 2))))Zero-Minute Flameout Baseline Check (t = 0 min)
Set Boil_Time B3 = 0 min: classic Tinseth gives 1 - EXP(0) = 0.0000 kettle boil utilization (brewers modeling hot whirlpool stands add a separate sub-boiling temperature isomerization factor)!
=IF(ISTEXT(E4), E4, ROUND(E4 / ((B2 - 1) * 1000), 2))Try the example
Use the original values or change them to test your understanding.