What it is
This calculator estimates a beer’s Alcohol By Volume (ABV) from its fermentable sugars, represented by the original and final gravity readings. The OG captures how much sugar is initially in the wort, while the FG shows how much remains after fermentation. Using the empirically derived factor 131.25 converts the gravity drop into a percentage of alcohol content. In addition to ABV, it reports the total absolute alcohol volume in liters, which is important for tax reporting, flavor profiling, and comparing batches across volumes. Accurate ABV estimation aids homebrewers in judging beer strength, adjusting recipes, and ensuring consistency.
How to use it
Enter the Original Gravity as a decimal (e.g., 1.050), your measured Final Gravity similarly, and the total batch size. Pick whether that size is given in liters or US gallons; the tool converts to liters automatically for internal calculations. After submission, view both the ABV percentage and the corresponding alcohol volume in liters – useful if you want to know how much actual ethanol has been produced.
Worked example
First compute the gravity difference: 1.050 – 1.010 = 0.040. Multiply by 131.25 to convert this drop into a percent alcohol: 0.040 × 131.25 ≈ 5.250 % ABV. Because the batch was entered in liters (volume‑unit = 0), no conversion is needed; the batch size is 5 L. The absolute alcohol volume equals batch × (ABV/100): 5 L × 0.05250 ≈ 0.2625 L, rounded to 0.263 L for display.
Inputs
- Original Gravity (OG): 1.05
- Final Gravity (FG): 1.01
- Batch Size: 5
- Volume Unit: 0
Result
- ABV (%): 5.25
- Alcohol Volume (L): 0.263
Frequently asked questions
What does ABV represent in brewing terms?
ABV (Alcohol By Volume) is the percentage of ethanol by volume in the finished beer. It indicates how strong a beer will taste and affects its flavor, mouthfeel, and perceived body.
How accurate is the 131.25 factor?
The 131.25 multiplier is an empirical approximation widely used for English gravity units (points). For most homebrew applications it yields practical accuracy; precise determinations may require laboratory analysis, but the calculator serves daily estimation needs.