Have you ever checked your pre-boil gravity and been several points under? Yeah, me too.
There are a number of ways to fix the problem, but my preferred method is to simply add some dry malt extract (DME) before the wort reaches a boil. I always keep several 1-pound bags of extra light DME on hand for making starters, so it’s easy to just dump them in.
After searching the web several times, I couldn’t find an easy-to-use DME gravity calculator to help me, so I made one myself.
Volume in Gallons: This should be the volume of wort that you’ll be adding the DME to, ideally right after your lauter is done and before you begin the boil. This is not the volume of finished beer, or a rounded-off batch size. You can use up to 2 decimal places in this number. (e.g. 5, 6.9, 12.25 are all valid.)
Gravity Point Increase Needed: For the sake of simplicity, this is just the difference in points using a whole number. We’re just removing the “1.” from the gravity numbers. For example, if you wanted your pre-boil gravity to be 1.055, but you only reached 1.050, then the difference would be 5 points (1.055 – 1.050 = 0.005 which becomes just 5 after removing the decimal and leading zeros).
DME to Add: This section lists the amount of DME you need to add to reach your desired gravity. The different units of measure are simply a conversion, so just use ONE of the results in the weight unit that your scale uses. For example, if I have 5 gallons and need 9 more points, I’m given the option of adding 1.02 pounds, OR 16.32 ounces, OR 462.66 grams.