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The Mythos Of The Beer Belly, or How To (Accurately) Guess The Calories In Your Beer

April 20, 2010

I hate the term beer belly. It’s so misleading. You get a ‘beer belly’ by consuming more calories than you use. It really is that ridiculously simple.

I could go on about how healthy beer is. I could say facts like beer is fat and cholesterol free, and that alcohol actually raises the level of good (HDL) cholesterol. Or I could say that moderate consumption of beer has been shown to lowers one’s chances of coronary heart disease by 30-40% and strokes by 20%. But I’m not. The health effects of beer has been since the dawn of civilization. Some people speculate that is why civilization started. To grow the grain needed to make beer.

This whole drinking beer gives you a beer belly thing just chafes me. It’s like saying giraffes are purple winged beasts that gorge upon human flesh and read Ayn Rand. They’re objectivists, don’t ya know. Maybe if we repeat this enough people will believe it. Giraffes are purple winged beasts that gorge upon human flesh and read Ayn Rand; and beer doesn’t intrinsically make you fat. Is it working?

Doesn’t look like it. So let’s get mathy and break down the facts. Growing a beer belly is all about calories in verses calories out. Food contains calories. Beer contains calories. Some beer contains 67 calories, but they tastes like corn flavoured water that can’t even get you buzzed. Some beers have over 1000 calories a bottle and have a cult-like following.

First I’ll cover the quick and dirty way of calculating the calories in your beer. A study done by Mr. Lester Hankin, and the The Connecticut Agricultural Experiment Station and the Excise Tax Division of the Connecticut Department of Revenue Service in the early 1990s. Might sound kind of dated, but the base ingredients of beer hasn’t changed since then. A sampling of 202 beers was completed. Regular, light, and non-alcoholic beers were all included. Luckily for me they calculated the average amount of calories per 100ml with 5% ABV. 43 calories. That works out to 8.6 calories per percentage per 100ml of beer.

Let’s try an example. First beer to catch my eye in my beer closest is a Chimay White Cap. It’s a 330ml bottle and 8% ABV.
(8*8.6)*3.3 = 227.04 calories

So about 9-10 of those in a day would give me my daily recommended intake of calories. With this little bit of information you can fairly effectively calculate how many calories you are consuming. This magic number doesn’t work for light beers due to the process required to make them.

To find out more exact numbers you need two of three numbers, and a few formulas, of course. They are ‘original gravity’, ‘final gravity’, or alcohol percentage. Having the specific and final gravity will give you the exact number. If you only have one of the numbers and the alcohol, in either weight or volume, you can work out the rest of the numbers you. Isn’t algebra great? That was rhetorical, as we all know it is.

The formula is:
calories per 100 ml = [(6.9 × ABW) + 4.0 × (RE - 0.1)] × FG

ABW = Alcohol by weight
RE = Real Extract
FG = Final Gravity

The 6.9 represents known value of 6.9 cal/g of ethanol and multiplying that by the ABW determines the calories given by the alcohol.

To calculate the ABW
ABW = (0.79 × ABV) / FG

The + 4.0 × (RE – 0.1) represents the amount of calories provided by the carbohydrates in the beer. 4.0 represents the known value of 4.0 cal/g for carbohydrates and the Real Extract represents the amount of fermented sugars.

To calculate the RE
RE = (0.1808 × °Pi) + (0.8192 × °Pf)
°Pi = the original gravity converted to degrees Plato
°Pf = the final gravity converted to degrees Plato.

Let’s use an example here. Yesterday I poured some extract, water and yeast in to a carboy. The hydrometer gave me an original gravity reading of 1.053. Let’s assume a standard attenuation of 75% is going to happen. That will give us a final gravity of of about 1.013. That gives us ºPi of 13.1 and a ºPf of 3.32.
ABW = (0.79 × 5.33) / 1.013 = 4.15%
RE = (0.1808 × 13.1) + (0.8192 × 3.32) = 5.1
calories per 100 ml = [(6.9 × 4.15) + 4.0 × (5.1 - 0.1)] × 1.013 = 49.27

Some kind gentleman made an online calculator that does all this math for you.

So there we have it. One way to estimate the calories based on ABV alone; and one way to get an accurate number, which is really only usable in home brewing.

Other maths:
ABV = (OG - FG) / 0.75
Specific Gravity to Plato
°P = (-463.37) + (668.72 × SG) - (205.35 × SG²)


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  1. This is all very interesting, Dave, but will beer make me more attractive to women or not?

  2. It works the other way around.

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  1. Calories in Your Beer, Now in Chart Form! « Beer in BC

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