**Adjusting**** pre-boil gravity up**

Let's say you are brewing a 5 gallon batch of beer. You have completed your mash and sparge and have collected the predetermined amount of wort (6.9 gallons). The only problem is you take a gravity reading and find that you have missed your target pre-boil gravity (1.040) by 5 points. Use this formula to calculate the amount of fermentable sugar to add to your wort.

*X = (Volume of Wort * (Target Gravity Points - Actual Gravity Points)) / Potential Points of Addition*

Of course, the variable here is the **Potential Points of Addition**. Each fermentable item has potential points. Check out this chart for the fermentable you are using. In this example, we are using DME which has a potential of 45.

Example:

X = (6.9 * (40 - 35)) / 45

X = (6.9 * 5) / 45

X = 34.5 / 45

X = .767

In this case we will need just over 3/4lb of DME added to our wort in order to bump up our gravity the needed 5 points.

**Adjusting pre-boil gravity down**

Let's say you are brewing a 5 gallon batch of beer. You have completed your mash and sparge. Your target pre-boil gravity is 1.040 and your target pre-boil volume is 6.9 gallons. You take a gravity reading of the full 6.9 gallons and find that your gravity is 1.042. Use this formula to calculate the amount of water to add to your wort.

**X**** = (Volume before dilution * (Actual gravity points – Target gravity points)) / Target gravity points**

Example:

X = (6.9 * (42 - 40) / 40

X = (6.9 * 2) / 40

X = 13.8 / 40

X = .345

In this case we will need .345 gallons (approximatly 44oz) of water added to our wort to reduce the gravity to 1.040.

**Alcohol by Volume ABV**

The basic formula most home brewers use for calculating the ABV of your beer is straightforward. The formula is as follows:

**ABV = (OG - FG) * 131.25**

It should be noted that the formula is less accurate as ABV increases. A more accurate formula requires knowing the alcohol by weight (ABW). The formula is as follows assuming you already know the ABW.

**ABV = (ABW * (FG / .794))**