How To Pick The Less-Bitter Beer Using a Bit of Science

You’ve probably noticed a number on craft beer labels, menus, or advertising labeled “IBU” (or “International Bitterness Units”).  This rating attempts to estimate the amount of the bittering compounds from hops that are dissolved into that beer.  A beer brewed with a small amount of hops has a lower IBU rating than one brewed with a lot of hops. 

This never explained to me why I could taste an India Pale Ale (IPA) rated at 70 IBUs and a stout rated the same, and find the stout to seem much less bitter than the IPA.  I wondered if perhaps the brewers of the stout miscalculated their IBU rating, or changed their recipe without updating the label.  The answer is much simpler than that.

As with many things in life, there is (or at least should be) a level of balance between the hops and the malt used to brew a beer.  Generally speaking, an IPA has a lower malt amount of malt than a stout.  This means that for any given IBU rating, the IPA will seem more bitter because there is less malt to balance out the hops bitterness.  The stout, having much more malt, needs a larger amount of hops to offset the natural sweetness of the malt used to brew it.  Thus 70 IBUs may not seem very bitter in a stout, but will be quite bitter in an IPA.

If you’re trying to guess which of two randomly selected beers will taste more bitter than the other without opening them, here are some ways to do that:

•  If the two beers are the same style (e.g., two pale ales), look at their IBU rating.  The one with the higher IBU rating will usually be the more bitter of the two.
• If the two beers are different styles (e.g., a Kolsch and a Dubbel), the IBU rating tells only part of the story.  If you can get the “original gravity” number for the beer and its IBU rating, you can use the BU:GU ratio (discussed in a moment) to identify the more-bitter beer.

As you gain some experience with the BU:GU ratio, you can determine approximately what ratio suits your beer taste.  That will help you pick beers to drink that you're more likely to enjoy.

Calculating BU:GU Ratios

If you have both an original gravity figure and an IBU figure, you can use the BU:GU rating to identify the more-bitter beer of the two.  The down-side is that many brewers do not share their original gravity figure.  Even those who share it don’t always report it the same way.   Rogue provides their original gravity as an unlabeled “degrees Plato” figure.  BrewDog provides it as a four-digit number.  Others provide it as a typical specific gravity rating like 1.056. 

Let’s look at an example.  I’m being offered BrewDog’s Punk IPA and Rogue’s Dead Guy Ale (a Maibock style beer).  Both are rated at 35 IBUs, but they’re different styles.  How do I compare them?

BrewDog’s web site says the starting gravity of Punk IPA is “1056” (which is usually reported as 1.056).  We discard the 1 and treat the rest as our gravity number (i.e., 56).   At 35 IBUs, its BU:GU ratio is 35:56 or 0.625.

Rogue’s web site says the starting gravity of Dead Guy Ale is 16 degrees Plato.  Using a handy web calculator, I convert that to 65.4 specific gravity.  This makes Dead Guy Ale’s BU:GU 35:65.4 or 0.535.

Since Punk IPA’s BU:GU ratio of 0.625 is much higher than Dead Guy Ale’s 0.535, we can be confident that Punk IPA is going to taste more bitter to us than Dead Guy Ale.

Estimating GU for a Beer

Although many breweries do not publish their starting gravity figures, you can estimate them.  While brewers can and do develop their own recipes for different styles of beer, in order for a beer to look and taste like an example of the style, the brewer can’t stray too far from the general recipe for the style.  For example, if you added dark malted barley to a wheat beer, it will no longer look or taste like one.  This need to stay “within a certain range” of the style gives us a way to estimate a beer’s original gravity so that we can compare it to another.

Following are some common beer styles and their typical average starting gravities:

• Belgian Dark Strong Ale: 92.5
• Belgian Golden Strong Ale: 82.5
• Belgian Single: 49
• Belgian Tripel: 80
• Belgian Witbier: 48
• Berliner Weisse: 30
• Biere De Garde: 70
• Bock: 70
• Bohemian Pilsener: 50
• Brown Ale: 47.5
• Brown Porter: 45
• California Common: 49.5
• Doppelbock: 77
• Dortmunder/Export Pilsener: 52
• Double Stout: 76
• Dunkel Weizen: 51
• Dusseldorf-style Alt:  47
• Eisbock: 104
• English Bitter: 35
• English Mild Ale: 33
• English Pale Ale: 50
• English Special Bitter (ESB): 42
• English Strong Ale or Extra Special Ale: 53
• Export Scotch Ale: 45
• Foreign Stout: 62
• Fruit Beers: 57
• German Pilsener: 47
• Heavy Scotch Ale: 37.5
• Imperial Stout: 85
• India Pale Ale (IPA): 60
• Kolsch: 46.5
• Light Scotch Ale: 32.5
• Maibock: 67
• Marzen: 58
• Munich Helles: 48
• Oktoberfest: 58
• Old Ale: 65
• Robust Porter: 52
• Russian Export Stout: 100
• Saison: 56.5
• Stout: 43
• Strong Scotch Ale: 78.5
• Sweet Stout: 56
• Vienna: 51.5
• Weizen: 51.5
• Weizen Bock: 72.5
• Witbier or Wit: 48

To use this table to compare two beers, use your calculator to take the beer’s listed IBU rating and divide it by the value in the list above for the closest style.