Alcohol ABV Calculator (OG to FG)
Estimate alcohol by volume from your original gravity (OG) and final gravity (FG). Great for beer, cider, mead, and wine fermentation tracking.
What this alcohol ABV calculator does
This calculator estimates Alcohol by Volume (ABV) using hydrometer readings: your Original Gravity before fermentation and your Final Gravity after fermentation. It is one of the most common and practical methods for homebrewers and small-batch makers.
If you enter a serving size, the tool also estimates pure alcohol in that serving and gives an approximate standard drink count. That helps with recipe planning, labeling, and responsible consumption.
ABV formula used
The calculator uses the classic brewing approximation:
ABV (%) = (OG − FG) × 131.25
Example: if OG is 1.050 and FG is 1.010:
ABV = (1.050 − 1.010) × 131.25 = 5.25%
How to use this calculator
- Measure your wort or must before fermentation and record OG.
- Measure again when fermentation is complete and record FG.
- Enter values exactly (typically to three decimals, like 1.062).
- Optionally add serving volume in ml (for per-serving alcohol estimates).
- Click Calculate ABV.
Understanding OG and FG
Original Gravity (OG)
OG reflects how much sugar is present before yeast fermentation. Higher OG usually means more fermentable sugar, and potentially higher final alcohol content.
Final Gravity (FG)
FG reflects what remains after yeast has converted sugars into alcohol and CO2. Lower FG generally indicates a drier beverage and stronger fermentation.
Apparent attenuation
The result includes apparent attenuation, which estimates how much fermentable extract was consumed. This is helpful when comparing yeast performance across batches.
Typical ABV ranges by drink style
- Session beer: 3.0%–4.5%
- Pale ale / lager: 4.5%–6.5%
- IPA / strong ale: 6.0%–9.0%+
- Cider: 4.0%–8.0%
- Table wine: 11.0%–14.5%
- Fortified wine: 15.0%–22.0%
ABV vs proof
ABV is a percentage of ethanol by liquid volume. In the US system, proof = ABV × 2. So a 40% ABV spirit is 80 proof.
Tips for more accurate readings
- Correct hydrometer readings for temperature if needed.
- Degas samples before measuring FG to reduce bubbles.
- Use calibrated equipment and clean test jars.
- Take two stable FG readings over 24–48 hours before bottling.
- For high-gravity or highly adjunct-based recipes, use advanced correction formulas if precision matters.
Frequently asked questions
Is this ABV exact?
It is an estimate based on a well-known brewing formula. For most practical homebrew applications, it is very useful. Laboratory analysis is required for exact legal-grade ABV.
Can I use this for wine, mead, and cider?
Yes. If you have reliable OG and FG values, this method works for many fermented beverages.
Why does FG need to be lower than OG?
During fermentation, sugars convert into alcohol and CO2, lowering density. If FG is not below OG, your inputs are likely incorrect or fermentation did not proceed normally.
Final note
This alcohol ABV calculator is designed for quick, practical estimates and recipe iteration. If you're sharing or selling beverages, always follow local labeling laws and drink responsibly.