Beer ABV Calculator (OG to FG)
Use your original gravity (OG) and final gravity (FG) to estimate the alcohol percentage (ABV) in your beer batch.
What this alcohol percentage in beer calculator does
This calculator estimates alcohol by volume (ABV), which is the most common way to describe beer strength. Entering OG and FG gives a quick and practical estimate of how much sugar was converted into alcohol during fermentation. It is especially useful for homebrewers, craft brewers, and anyone tracking recipe consistency.
How ABV is calculated from OG and FG
The core idea
During fermentation, yeast consumes sugars and produces alcohol and carbon dioxide. As sugar is consumed, gravity drops. The difference between original gravity and final gravity tells you roughly how much fermentable material was converted.
- OG (Original Gravity): Gravity reading before fermentation starts.
- FG (Final Gravity): Gravity reading after fermentation is complete.
- ABV: Alcohol by volume as a percentage.
Formulas used in this calculator
The calculator shows two ABV estimates:
- Standard formula: ABV = (OG − FG) × 131.25
- Refined formula: ABV = (76.08 × (OG − FG) / (1.775 − OG)) × (FG / 0.794)
The refined formula is commonly used when brewers want a little more precision across a wider gravity range.
Quick example
Suppose your IPA starts at 1.062 and finishes at 1.012:
- Gravity drop = 1.062 − 1.012 = 0.050
- Estimated ABV (standard) ≈ 6.56%
- Refined estimate will be close, typically within a small fraction of a percent
This gives you a realistic expectation for labeling, recipe planning, and style comparison.
How to get better gravity readings
1) Calibrate your measuring tool
Hydrometers and refractometers can drift over time. A quick calibration check in distilled water can improve your accuracy.
2) Correct for temperature
Hydrometers are usually calibrated at a specific temperature (often 60°F or 68°F). If your sample is warmer or cooler, use a correction chart or software correction factor.
3) Degas final samples
Carbon dioxide bubbles can cling to instruments and distort FG readings. Swirling or gently stirring your sample helps remove gas.
4) Take readings at the right time
Take OG before yeast is pitched. For FG, wait until gravity is stable for at least 2–3 days to confirm fermentation is complete.
Typical ABV ranges by beer style
- Light lager: 3.5%–4.5%
- Pilsner: 4.5%–5.5%
- Pale ale: 4.5%–6.2%
- IPA: 5.5%–7.5% (and higher for double/triple styles)
- Porter/Stout: 4.5%–8.0%
- Belgian strong ales: 7.0%–11.0%+
Why your estimated ABV might differ from lab results
Calculator results are estimates. Professional labs can report alcohol content more precisely using specialized methods. Small differences are normal and can be caused by:
- Instrument accuracy and calibration
- Temperature correction errors
- Residual fermentables and yeast behavior
- Sampling technique and timing
Frequently asked questions
Is ABV the same as proof?
No. In the U.S., proof is roughly double ABV. For example, 5% ABV beer is about 10 proof.
Can I calculate ABV without OG and FG?
Not accurately. You can estimate from style guidelines, but OG and FG are the best practical inputs for homebrew-level ABV calculations.
What if my OG is less than or equal to FG?
That usually indicates a data entry mistake or unfinished fermentation. The calculator will flag this, since ABV cannot be computed correctly in that case.
Bottom line
If you brew beer, knowing how to calculate alcohol percentage gives you better control over recipe design and final product quality. Use the calculator above, record your readings carefully, and compare batches over time to dial in consistency.