3 Ways To Measure Beer Bitterness Ratios

The balance between sweet malt and bitter hop flavours is a defining characteristic of most beer. It’s essential you think about this if you want to control the taste of your home brew.

But how can you measure this balance?

beer bitterness ratios

Beer recipes usually contain target original and final gravities alongside International Bittering Unit (IBU) values.

Gravity describes the quantity of sugar required, usually produced with malted barley, while IBUs are an indication of the bitterness provided by hops.

(If you’re already lost check out this page describing the basic ingredients used to make beer).

Although this information can help you determine quantities of malt and hops, it doesn’t tell you anything about balance.

That’s what is actually important: whether a beer tastes bitter or not.

Balancing Beer

To understand this difference think of two beers.

One is high gravity with lots of hop bitterness. The second has half the gravity with the same amount of hops.

To taste, the second is twice as bitter. The effect of the hops is stronger.

This is where the bitterness ratio comes in. It describes the relationship between bitterness and gravity, regardless of the actual numbers.

It tells you whether a beer is broadly bitter or broadly sweet.

Calculating Beer Bitterness Ratios

There are several ways to calculate bitterness ratios.

The simplest, and most frequently used, has been explained by Brad Smith.

He describes a method that compares original gravity with bittering units using this formula:

{IBUs}/{OriginalGravity}={Bitterness Ratio}

This is the BU:GU ratio.

I’ll use this porter recipe to show you how it works. The beer has:

  • Original Gravity 1.056
  • IBUS 30

First convert the gravity figure into gravity points. That’s a simple matter of removing the 1 and multiplying by a thousand.

Use this formula:

({Original Gravity}-{1})x{1000}={Gravity Points}

In my example beer this comes out as:

({1.056}-{1})x{1000}={56}

Now use the first formula to work out your bitterness ratio:

{IBUs}/{OriginalGravity}={Bitterness Ratio}

{30}/{56}={0.54}

0.5 is considered average. Beers with a bitterness ratio above this are more bitter, and those below are sweeter.

This porter then, is slightly more bitter than usual.

So far, so good. This tells us about the bitterness ratio, but what you really need to know is how this can help you design beer recipes.

Bitterness Ratios For Different Beer Styles

The BJCP has published style guidelines for more or less every beer from across the world.

Although brewing within such rigid boundaries is mainly for those entering competitions, the document is a very handy port of call when planning your own beer recipes.

The guide contains detailed statistics  (bitterness, gravity, alcohol and colour) which quickly give you a feel for each style.

When looking at bitterness ratios, you’re interested in original gravity and bitterness. The guide gives these as a range so first you have to work out the average.

Let’s say you want to find out the bitterness ratio of the average brown porter.

Original gravity is between 1.040 and 1.052:

original and final gravities for a typical porter

An average of 1.046, or 46 points.

And the IBUs are between 18 and 35:

ibus for a typical porter recipe

An average of 26.5.

With this you can work out the bitterness ratio:

{26.5IBUs}/{46GravityPoints}={0.58}

My porter recipe, with a ratio of 0.54, is slightly less bitter than average.

Knowing this you may decide to add a few more hops to compensate, if you’re shooting for dead on style.

Proof That Bitterness Ratios Are Worth Bothering With

Notice that if you had just compared the raw number of bittering units you would have guessed that my porter was more bitter than most. It has 30 IBUs against the 26.5 IBU average.

Bitterness is relative to the sweetness of malt, and IBUs alone don’t take that into account.

Beer Bitterness Ratio Chart

You can use this chart to compare each style:

beer bitterness ratio bu:gu

If you prefer, there is a pdf here.

Relative Bitterness and the BU:RE Ratio

As I was putting this page together I began thinking that something’s not right.

Brad Smith points out that the bitterness ratio alone doesn’t convey the full picture. Roasted malts also have bitter flavours that alter the taste, for example.

But the thing that was bugging me was the lack of consideration of attenuation, which is another way of saying the amount of sugar that’s consumed during fermentation.

Using another two hypothetical beers as an example:

  1. O.G. of 1.100, FG of 1.030, IBUs 50
  2. O.G. of 1.100, FG of 1.010, IBUs 50

The only difference is the final gravity, the sugar left in the beer after fermentation.

Beer 2 would taste more bitter because it has less residual sweetness, yet the BU:GU ratio would be the same:

{50IBUs}/{100GravityPoints}={0.5}

After digging around I discovered that I wasn’t the only one to have noticed this. In fact, the Mad Alchemist has proposed an interesting alternative system for measuring bitterness ratios.

His method compares IBUs with gravities using this formula:

{IBU}/{(0.1808 * O.G.)+(0.8192 * F.G.)}= {BU:RE}

The complicated looking bottom line uses the formula for calculating real extract, an accurate way of measuring attenuation.

This time gravity is in °Plato which can be determined like this:

{Specific Gravity}/{4}={Plato}

The alternative ratios are on a scale of 1 to 10.

This is how that compares with the BU:GU ratio:

beer bitterness ratio bu:re compared with bu:gu

Bear in mind that I multiplied the BU:GU ratio 10 to make comparison easier.

The overall pattern is similar but the beers you’d expect to be more bitter, such as Imperial IPA or Special Bitter, now have a higher bitterness ratio.

Although it still doesn’t allow for other factors such as astringent roast malt, it’s a more robust method of calculation.

My Own Beer Bitterness Ratio

Before I found the Mad Alchemist’s (convincing) technique I had already developed my own bitterness ratio to deal with my doubts about BU:GU.

It’s a half-way point between the two.

Like BU:GU it works with simple gravity information from the style guide, but it takes into account final gravity as well.

{IBUs}/{Original Gravity-Final Gravity}={HBM Bitterness Ratio}

Here’s how that comes out in chart form:

Beer bitterness ratio: Gravity Difference Ratio

You can get a pdf here.

The numbers are higher, but the pattern between beers is similar and this ratio deals with differences in final gravity.

I’m still testing this when I brew.

What do you think of the method? Let me know in the comments.

Using The Bitterness Ratios

The main thing to remember with all of this is that you’re controlling the balance of beer flavours between sweet and bitter. It’s up to you where you want your beer to fall on the scale.

As long as you understand what the figures mean and can relate them to beer, that’s OK.

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Comments...

  1. patrickjdempsey

    I took a look at the numbers in your last chart. It looks like your HBM numbers can convert down to near equivalents to BR like this:

    (HBM+0.01)/1.3 ~ BR

    This is interesting because your HBM number can be calculated from ABV:

    ABV/0.131 = OG/FG

    So putting that together:

    IBU / (((ABV/0.131)+0.01)/1.3) ~ BR

    • John

      Hi, thanks for chiming in.

      Having checked a few of the ratios, it does seem that the relationship with BR (BU:GU) is only approximate (unless I’m missing something, which is quite possible), so I’m not sure how much sense it makes to covert the figures. It seems to me that you may as well keep the HBM number if they’re different anyway.

      I suppose the benefit is that it would give a number similar to BU:GU, which is fairly well known.

      But it is interesting to see a relationship between alcohol levels and bitterness ratios.

      Can I check, do you mean ABV/0.131 = OG – FG (Derived from ABV = (Original Gravity – Final Gravity)x0.131), rather than OG/FG.

      If you do, to simplify your equation you could use the HBM unit (for better or worse) and get this bitterness ratio, in terms of alcohol:

      BR(ABV) = IBU/(ABV/0.131)

      In fact you could take it even further and remove the 0.131 as that’s a constant, but then you’d be using an entirely new scale again.

      Sorry if I’ve misinterpreted your suggestion! Thanks again for your interest.

      • patrickjdempsey

        Yes, sorry about that typo! I meant OG – FG. I understand that this is only an approximation, but it is interesting to use ABV from the consumer end as opposed to the brewer end where you may not have OG and FG but ABV is ubiquitous.

        I mostly wanted to point out the conversion factor to get your HBM numbers to compare directly to BR numbers:

        (HBM+0.01)/1.3 gets to within 1-2% accuracy for *most* beers to BR.

        Since 0.5 is considered the “balance” point for BR, doing this conversion should allow you to use the HBM number and directly compare your results to BR numbers.

        • John

          Yes, I can see how that would be more use to non-brewers. It’s handy that there’s such a simple (if approximate) substitution that brings ABV into the ratio.

          And you’re right, it also makes sense to have numbers that are directly comparable with typical bitterness ratios as well.

          Thanks again for your input!

  2. Nuno

    Please compile all your posts into a book.

    • John

      Perhaps one day.

      Cheers.

  3. Great to see others looking for better ways to do things! I plan to run some more numbers and adjust based on other factors like SRM in the next iteration of BU:RE.

    I’d eventually like to be able to make something where you just plug in some numbers and get something reasonably close to the truth. The current methods most people use are ballpark at best. I’d like to get you on the field.

    • John

      Thanks. I’ll watch out for and read with interest the next version.

  4. Mauricio

    I have long been trying to solve the formula that uses the Windows software Brewers Friend for calculating the Balance Value.
    Unfortunately it is not none of the above.
    Can you help me?

    • John

      Sadly not, I’m afraid. Sorry.