So it’s worth taking his work and formula very seriously. Tinseth had “access to some handy tools and knowledgeable friends at the USDA hop labs and the Flavor Perception labs at Oregon State University,” and he has “had quite a few worts and beers analyzed.” His formula is very widely used, presumably because it does as good or better a job at predicting bitterness levels compared with other available formulas. If one takes a standard formula for predicting IBUs, such as Tinseth’s, hops additions at flameout contribute nothing to the final IBU measurement. The SMPH model incorporates the post-flameout technique described here. While the technique described here is still correct, I’ve since developed another IBU calculator (called SMPH) that accounts separately for the contribution of isomerized alpha acids and auxiliary bittering compounds to the IBU. John Koopmans has made an implementation of the mIBU method available in an Excel document.

I’ve created an on-line calculator for the mIBU method here: with a description of this calculator in the blog post An On-Line Calculator for the mIBU Technique. This new metric is referred to as “maximum IBU” (or “mIBU”), for reasons explained below. This blog post proposes a modification to the Tinseth IBU formula to account for hops added late in the boil and/or at flameout. This is in conflict with widespread experience, which shows that adding hops at flameout does add significant bitterness. The predicted IBU contribution when adding hops at flameout is usually zero.

Beersmith 3 xp