The Easy Way to Estimate the Calories in Beer

Is your favorite post-ride pint wrecking your diet? Use this smart, quick approach to find out.

BY JOE LINDSEY APRIL 12, 2016 

 

The next time you go drinking, take a second to figure out exactly what you're gulping down.PHOTOGRAPH COURTESY OF ALAN LEVINE/FLICKR

Few things taste quite as good after a long ride as beer. But whether your tastes trend toward light-bodied pilsners or hop-bomb Imperial IPAs has a lot to do with what you’re ordering, and we aren’t just talking about flavor.

All alcoholic drinks have calories in them, byproducts of the sugars used in fermentation (and, to a degree, the sugars left over from the fermentation process). But all beers are not created equal calorically. Beers range from well under 100 calories per 12-ounce serving, for light beers, to 500-plus-calorie bombs for something like Dogfish Head’s highly regarded 120-Minute IPA.

So those two session IPAs you just knocked back at happy hour? That could mean 300 to 350 extra calories—calories you have to account for in your daily intake if you’re trying to lose or maintain weight.

The exact number of calories comes down to two factors: how much sugar was in the wort (the liquid from the mash of sprouted grains and water used in the first step of the brewing process); and how many unfermented sugars are left after brewing. The scientific names for those values are, respectively, the original gravity (starting sugar) and final gravity (unfermented residual sugars at the end of the brewing process).

The amount of calories from residual sugars varies by individual brew just as alcohol content does, but generally it’s 30 to 40 percent of a beer's total calories. To get the exact calorie count of a beer, you’ll need to know both the original gravity and final gravity. (Hint for the soused: FG is always the lower of the two numbers.)

Here's how to calculate the exact number of calories in your beer:

1. Calories from alcohol: 1881.22 x Final Gravity x (Original Gravity — FC) / (1.775 — OG)
2. Calories from leftover sugars: 3550 x FG x (.1808 x OG) + (.8192 x FG — 1.0004)
3. Add both figures for total calories

For most of us, beer + complicated equations = faulty math. There are a few sites and apps that will do the calculations based only off of OG and FG, but unless you’re at a taphouse or brewpub that publishes those numbers on the tap board, you’re outta luck.

Fortunately, there’s an easier way: estimate based on alcohol content. Pretty much every bottle, can and beer list out there has ABV listed for each brew these days. And, when you calculate a number of beers, across various styles, through the above OG-FG equation, you’ll find that, per ounce, there’s about 2.5-3 calories for every percent of ABV. For most beers, it’s 2.5, but for full-bodied beers like most stouts, it’s closer to 3, hence the range.

Estimating calories in beer requires a much simpler formula: ABV x 2.5 x ounces per serving

So: A four-percent pilsner has 12 calories per ounce; a 12-ounce serving will have 120 to 144 calories. That nine-percent Imperial IPA? A wee bit heartier, as it clocks between 270 and 320 calories.     

To be sure, this is just an estimate, and you probably noticed how the caloric margin of error increases with higher-alcohol beers (use the 3x multiplier with full-bodied beers, or to ensure you’re not underestimating). But it’s accurate enough for the goal at hand: to be honest with yourself about how many calories you’re really drinking, and whether that—and not your Strava activity—is the real reason you’re having trouble losing those last few pounds and keeping them gone.

If you’re still fuzzy on math, here’s your drinking game plan: That myth about Guinness draught being the lowest-calorie beer that’s not a “light” beer is absolutely true. Although its dark color might fool you into thinking it’s a full-bodied beverage, it’s just 125 calories per 12-ounce bottle.