IBU Calculator Using the SMPH Method

This page provides a calculator for predicting IBUs using the SMPH method. The techniques used in this method are described in the blog posts "A Summary of Factors Affecting IBUs" and "IBUs and the SMPH Model". This method accounts separately for the contributions from isomerized alpha acids (IAA) and "Auxiliary Bitter Compounds" (ABC or nonIAA). It is based in large part on work published by Val Peacock, Tom Shellhammer, and Mark Malowicki, as well as my own experiments. This calculator takes into account utilization from any hop stand or whirlpool, as well as the time it takes to cool the wort using an immersion chiller, counterflow chiller, or ice bath. Other optional adjustments include an alpha-acid solubility limit, adjustment of IBUs based on wort pH, adjustment of IBUs based on wort clarity and krausen loss, adjustment based on the use of hop pellets instead of whole cones, and IBUs from dry-hopping.

For "boil or steep time" with kettle additions, specify the number of minutes before flameout. A negative value indicates time after flameout. For example, a value of 10 means that the hops are added at 10 minutes before flameout (during the boil). A value of 0 indicates a flameout addition. A value of -10 means that the hops are added to the hot wort at 10 minutes after flameout. Post-flameout kettle additions can be made during a whirlpool or hop stand, or while the wort is being force cooled. For dry-hop additions, specify the number of days of dry hopping.

Default values are shown in grayish-red. The defaults should yield reasonable results for most homebrewing scenarios. The temperature-decay defaults are based on the wort volume, kettle diameter, and kettle opening diameter. For most homebrewers, the kettle diameter and the opening diameter are the same (with an uncovered kettle). The "exponential decay" function is probably somewhat more accurate than the "linear" function, but the linear function is easier to conceptualize (e.g. a decrease of 1.74°F per minute).

To get back to a default value, enter 'd'. To save settings to a text file or load them from a file, use the "Save" and "Load" buttons near the bottom of this page. To clear all settings, use the "clear" button at the bottom of this page.


Input Units: metric or U.S.customary (e.g. gallons, ounces)
Boiling Point of Water (°F):

Kettle Diameter (inches): (for wort exposed surface area)
Kettle Opening Diameter (inches): (often same as kettle diameter)

Boil Time (minutes):
Evaporation Rate (G/hr):
Wort Volume (G @ room temp.): pre-boil or post-boil volume
(Post-Boil) Original Gravity:
Wort/Trub Left in Kettle (G):
(Partial Boil) Added Water (G):

Number of Hop Additions:
Global IBU Scaling Factor:
Default Hop Form:

Apply alpha-acid solubility-limit correction
Apply pH correction with wort pH = pre-boil or post-boil
Model IBUs of dry-hop additions (this model provides only a rough approximation)
Specify hop alpha-acid decay using: storage conditions freshness factor

Post-Boil Temperature Decrease:
Post-Boil Wort Temperature Decay Function: linear or exponential decay
   temperature (°F) = TO_BE_CHANGED

Whirlpool and/or Hop Stand Time: minutes
quickly cool to °F, then hold at this temperature during hop-stand time

Forced Cooling Method:
  immersion chiller (exponential decay factor: )
  counterflow chiller (wort flow rate: gallons/min)
  ice bath (exponential decay factor: )

Fermentation and Conditioning:
Volume at Pitching (G):
Wort Clarity into Fermentor:
Krausen Loss:
Yeast Flocculation:
Finings: tsp of
Filtering (micron rating):
Beer Age (days at room temp.):


Save and Load:

Save to File:
Load from File:


1.0.1: (2018-Nov-22 to 2021-Aug-28) Initial version.
1.0.2: (2021-Sep-04) Bug fix in AA concentration when dry hopping.
1.0.3: (2021-Oct-05) Bug fix, and don't reduce solubility limit with temperature.
1.0.4: (2021-Nov-25) Minor updates.
1.0.5: (2022-May-18) Storage duration of 0 months is valid.

Navigate to:
top of page
AlchemyOverlord home page


Copyright © 2018-2022 John-Paul Hosom, all rights reserved. All product and company names are trademarks™ or registered® trademarks of their respective holders. Use of these names does not imply any affiliation with, endorsement of, or endorsement by them.

While I hope that you find this page useful, I make no guarantees about the accuracy or suitability of the results. Predicting IBUs is a bit of a "black art", because there are so many variables and there is so much variability. The only way to really know the IBU level of a beer is to have it professionally tested, which is something I highly recommend. Cheers!