The tool above is designed to help the home brewer calculate the predicted original gravity and color of a specific beer recipe. The same results can be obtained by entering the fermentable ingredients into the more elaborate Brewer’s Recipe Calculator found elsewhere on this site.
To begin, enter the recipe’s Batch Size, Fermentation Tank Loss, and Boil Kettle Loss. I could have written the calculator to just ask for a specific post-boil batch size but system losses are often forgotten and can skew the final results.
I have also included a Brew House Efficiency factor into the calculator. Since there are really no home breweries that can extract 100% of the fermentable sugars from the grains of a recipe, this factor can be used to get a more accurate Predicted Original Gravity. My home brewery usually runs at about a 77% efficiency.
Next, it will be necessary to enter the Fermentable Ingredients necessary for the recipe you are brewing. When this is done, the calculator will tell you the Total Grain Bill in pounds as well as a Predicted Original Specific Gravity based upon your Brew House Efficiency. The calculator will also tell you the Total Non-Mashed Ingredient Bill which includes such things as honey and malt extracts. You will also get to see the Malt Color Units, SRM, and approximate Beer Color in graphical form.