Knowing how much alcohol is in your home-brew beer is important for many reasons. Luckily, if you have a hydrometer handy, it’s really easy to measure exactly how much alcohol is present in your home-brew.
So how exactly do you measure the alcohol content of your home-brew? In order to accurately calculate the alcohol content of your beer you need to subtract the Final Gravity (density after fermentation) from the Original Gravity (density before fermentation) then multiply the result by 131.25. Formula: (OG -FG) x 131.25. Example: (1.050 – 1.010) x 131.25 =5.25 ABV%
It’s one of the questions that many of us ask when drinking a beer, how strong is it? Of course, we mean how much alcohol it has in it.
Whether you are looking for something to really knock your socks off like a Belgian Trippel or something like a light beer so that you can get up for work in the morning, ABV matters!
In this article I have gone not only answer how to calculate the alcohol content of your home-brew beer, I have also tried to think of some other question you might have and have researched the answers to them too. Read on for more details on measuring ABV in beer.
What is alcohol by volume exactly and how is it determined?
ABV stands for alcohol by volume and is an international measurement of the alcohol content in drinks.
It actually measures the total pure ethanol content in milliliters per 100 ml (around 3.4 fl oz) at a temperature of 68°F (20°C).
As alcohol is less dense than water, the closer the final gravity to 1.099 the higher the ABV is going to be. As a brewer, we can determine the ABV of our home-brew beer by measuring its specific gravity at certain times of the brewing process.
How to measure your Original Gravity and Final Gravity
In order to find out your ABV, you need to know your OG and FG (original gravity and final gravity). By this, we mean just the density of your wort or beer at two particular times during the brew.
Original Gravity:
Most people will say that you want to take your original gravity reading just before you pitch your beer. However, it is really advisable that you take several readings during different stages of the process such as post-mashing, during the boil and just before the end of the boil. Although hydrometers are a good instrument, to save wasting wort and time, consider investing in a refractometer (see my recommended gear).
As a general rule for a pre-pitching sample, this measurement should be taken when the beer is between 80°F-68°F (26°C-20°C) and when the wort is in the fermenter. Take a small sample of your wort and use a hydrometer or refractometer to gain a density measurement.
Make sure that you are reading the hydrometer correctly and write the information down somewhere.