What Is Original Gravity?

As Mythbusters’ ballistics expert, Alex Jones, has said, “Remember kids, the only difference between screwing around and science is writing it down.”

- Garrick Van Buren

Beer 101

During the brew day, one of the most important things to write down and one of the very last things to write down is Original Gravity. Original Gravity dictates whether the desired ABV will be achieved in a brew. It dictates whether the hop additions will provide the desired balance. It determines whether or not the brew day went as planned. Ultimately, it’s a measure of how well the brewer knows their brewery.

Gravity is a key measure in physics and petroleum as well as brewing and winemaking. In physics gravity is the force bringing objects together. In the contexts of petroleum and fermentation, gravity is the measure of a liquid’s density relative to water at a specified temperature. Within brewing and winemaking, the difference in density is a result of dissolved, fermentable sugars. Each increment (1/1000th) on the specific gravity scale represents a .1 percent increase in density - a 1.100 specific reading indicates a wort that is 10 percent denser than water. Most 5 percent ABV beers have an original gravity around 1.050. Bigger beers like American Barleywines and Imperial Stouts can surpass 1.100 with smaller beers like an American Light Lager or Berliner Weisse rarely exceed 1.030.