HopsWhilst I am not always active here on the blog, I am very active on social media and especially Facebook. I am honoured to be a part of the admin team for the UK Craft Beer Network and the associated UKCBN Facebook group, which helped a lot of the 1,000+ members it gained in its first year with their brewing and beer related questions. I am also a member of several other brewing related groups including the Black Country Home Brew Club where there was a question which was the inspiration for this post. The question was about bitterness in homebrew and how to reduce the bitterness in this persons’ next batch. This lead me to thinking that here was a subject which could probably use a bit more of an explanation than would fit in a Facebook post.

Not all brewers, or even all home brewers will use actual hops when brewing a beer. There are pre-hopped kits, extracts and other ingredients available which can be used, but this post is all about using actual hops, so please excuse me whilst I gloss over those other methods and sweep them under the rug for now.

Chemical structure of humulone, the most prevalent alpha acid in hops
Chemical structure of humulone, the most prevalent alpha acid in hops

Before you can understand how to increase or reduce the level of bitterness in a batch of beer, it is important to know where that bitterness comes from. At the most basic level, the answer is it comes from the hops, but that is like saying money comes from the bank. It explains it all without explaining anything. I am aiming this as a basic introduction level so I will try not to get too technical.

The bitterness in beer actually comes from iso-alpha acids which are generated when Alpha Acids from hops are isomerised by heating them in a solution. Put simply, you heat the hops in your wort and the action of heat and time will create the bitterness that you look for in beers. It is important to realise it does take both heat and time, so you can adjust either of those and immediately you have changed the level of bitterness in your brew.  Here are the main methods of varying the bitterness level of your beer.

Hop Quantity

This is probably the most obvious way of adjusting bitterness. as long as you have heat and time, then more hops = more bitterness and vice versa.  However bitterness is not the only affect of changing the quantity. It will change the flavour, quality and quantity of your beer, more hops absorb more fluid meaning less finished beer. Large quantities can cause vegetal, grassy or herby flavours, which may or may not be desirable in the beer style you are brewing.

Alpha Acid level

When using hops, the normal method is to take your batch of beer you are brewing and either boil the whole lot, which is known as a full batch or full volume boil, or alternatively, take a portion of your batch and boil that. Whilst the beer is boiling many different types of ingredients can be added, including our item of interest, the hop.

Over the years there have been all types of hop varieties both carefully crafted and cultivated or just found growing wild. Each of these different varieties have different characteristics. The appearance, feel, smell, flavour and components of each of these varieties can be either very similar or very different. When it comes to bitterness, we are especially interested in the Alpha Acid levels in any particular variety you intend to use. The higher the levels of Alpha Acid, which is commonly referred to as AA and shown as a percentage, then the higher the bitterness you will be able to extract from them. There are many different acids, but for the sake of this introduction, we will not go any further down that rabbit hole and just refer to AA. To keep things simple, we will assume you are using fresh hops from the previous years harvest, but if not, then you will need to find out the HSI or hop storage index to see how quickly you lose that Alpha Acid in storage as some hops can lose as much as 50% of their original alpha acid levels over a year depending on how they are stored.

Very roughly speaking if you take a 5% AA hop to use for bittering your beer, then all other things being equal, you should need to use twice as much to get the same level of bitterness as you would if you were using a 10% AA hop. Not all hops are created equal and there are variables and variations, which depend on several factors but as a working simplification, that just about covers it. If you decrease the AA% of the hops you use and keep everything else the same, the bitterness goes down and vice versa.

 Format or presentation

As well as hops being available in all sorts of different varieties and AA levels, they are also available in different formats. You can get Whole leaf hops, which are the full cones taken from the hop bine. There are pellets in different grades, the most common is the T90 pellet but there is also a much less widely available T45, then there are plugs or hop oils / extracts. Which of these you use will have a big impact on the concentration of alpha acids in the hops and also the utilisation or how much of the bitterness forming compounds you get out of them.

The hop oil / extracts are the most highly concentrated format available so a very little of this goes a long way.  Next the T45 and T90 pellets. As these are highly processed and finely ground hops compressed into a pellet, once they get wet, they dissolve into small flakes meaning that it is much easier to get more out of them than it is for the plugs, which are compressed whole leaf hops, or the unprocessed whole leaves themselves. This is much the same way that finer ground coffee or finer shredded tea leaves are easier to extract more of their goodness than when it is very coarse. Whilst it is not commonly used as a method of controlling bitterness, you need to be aware that if you change the format from leaf on one batch to pellet on the next it is certainly going to affect the bitterness in your finished beer and you need to adjust for this. The differences between each of the hop formats


Every brewer and indeed every beer is slightly different when it comes to how it is brewed. I would go so far as to say most home brewers perform a 60 minute boil. This is where you get your wort up to a boil and then add the first or bittering hop addition. These are boiled in the wort for a full 60 minutes before turning the boiler off, optionally adding other hops at different periods throughout the 60 minutes.  As I mentioned earlier it takes both time and heat to create the iso-alpha acids from hops to create your beer bitterness. If you boil your hops longer then, up to a point, you will get more bitterness out of them. This does have decreasing returns though, you wont get twice the bitterness for boiling twice as long but you will get more bitterness. This gives you another way to adjust bitterness. If you boil the hops for a longer time you get more bitterness, or shorter you get less. As the time gets increasingly shorter, you will find that you get much smaller amounts of bitterness but you get more flavour from the hops as it is not driven off by long periods of boiling, and then when you get down to boiling for 5 minutes or less you will only really be extracting aroma from the hops. This is why, depending on the beer style, people do multiple additions of hops at different times.


Without heat you can add loads of hops without increasing the bitterness. This is what happens when people dry hop their beer, which is simply putting hops in, a normally room temperature or colder, beer. They end up getting heaps of flavour and aroma from the hops without extracting any bitterness. Adding hops after the turning the boiler off, what’s known as flameout, or indeed after you have let it cool down a bit, and leaving them to steep in the hot fluid is another common technique of getting the flavour and aroma without adding much bitterness. It wouldn’t make a very good beer if you didn’t have any bittering but you can certainly use this technique to pack a whole lot of hop wallop in a beer without turning it into something that puckers your face like an acid drop by excessive bittering.


There are actual units of measurement for bitterness levels in beer, one of the most commonly recognised is the IBU or International Bitterness Units Scale. This number may be able to tell you exactly how bitter your beer is, but we are humans and our sense of taste is a complex thing. Whilst most of us have no trouble detecting bitterness, there are many other flavours that affect how bitter we perceive something to be. If you increase the sweetness of a liquid it will seem to offset some of that bitterness so that it will no longer taste as bitter as before, whilst the actual measured bitterness is the same. This means when we talk about bitterness in beer, you have to remember it is how we perceive that bitterness as a whole alongside the other flavours in the beer.

The problem, or actually, it’s the great thing about beer, but problematic in this case, is that we can’t just add a few spoons of sugar into the beer to sweeten it like we would a cup of tea. Yeast feed off sugar and turn it into alcohol, so if you add extra of most types of sugar then over time, you will find your yeast just eating up that sugar and you have a stronger, but no sweeter beer than you started with. You could kill off, or filter out all your yeast, but that would certainly have an impact on the shelf life and flavour of your beer. What you can do, is add more un-fermentable sugars. This can be from mashing your grain at a higher temperature, adding more highly kilned malts like dark crystal or chocolate malt etc. or adding specific ingredients as these will leave more longer chain molecules in your beer that brewers yeast just can’t eat. The side effect of this is that your beer tastes sweeter and then you will not notice the bitterness as much,.  Whilst it may not be acceptable in all beer styles, some styles have this sweetness as one of the key characteristics of the style. This means you can change how bitter the beer tastes even without changing anything to do with hops.

Kernel - London Sour


Now you know some of the different ways you can affect your bitterness levels, you will need some way to quantify it. It’s easy to say to use less hops or more time etc., but how much more or less will give you a certain result? This is where some brewing software comes in. There are a lot of tools available to the brewer, some are free and some you have to buy. You can use something free like Beer Engine, something you trial, or pay for like Beersmith or any number of brewing calculators or spreadsheets to work out what effect any of these changes will have on your next batch of beer. My personal preference is for Beersmith, but something else may work better for you.

Please feel free to join either of the Facebook groups mentioned above if you have any questions. There are a whole range of folks in the groups, from pro brewers and home brewers through to people who just love great beer. You will however always find them supportive and someone, normally with years of experience is more than happy to help you.



Sarah is an experienced home brewer, a qualified BJCP beer judge, organiser of the Welsh National Homebrew Competition and sometimes Brewtuber under her home brewery name, Daft Cat Brewing