Understanding original gravity and final gravity
Original gravity captures dissolved sugars before fermentation. Final gravity captures the remaining density after yeast activity slows and readings become stable.
Alcohol by Volume Calculator
Calculate the ABV percentage of any homebrew or mixed drink.
Gravity readings
Enter readings as specific gravity values, such as 1.050 and 1.010.
Reading before fermentation, commonly called starting gravity.
Reading after fermentation, once the value has stabilized.
Estimated alcohol by volume
5.25%
Common beer range
Apparent attenuation
80.0%
Gravity drop
0.040
Estimated alcohol per serving
Add serving size
Estimated batch alcohol content
Add batch size
Formula used
ABV = (OG - FG) x 131.25
Copy result
Copy the ABV estimate, attenuation, gravity drop, serving estimate, and formula.
Formula note
The calculation uses the common gravity based approximation for beer and cider.
Accuracy disclaimer
Small reading errors can change the result, especially for higher strength batches.
Hydrometer note
Check your hydrometer calibration temperature before comparing readings.
Local calculation
Inputs are processed in your browser. No external API is required.
Brewing estimate
Fermentation behavior, yeast health, and recipe design can influence the finished result.
Dynamic brewing insights
Strength range
This range is common for many lagers, ales, and ciders.
Fermentation status
Final gravity appears within a typical finished range for many fermented drinks.
Measurement check
For better accuracy, correct hydrometer readings for temperature and correct refractometer readings after alcohol is present.
ABV reference table
0 to 3%
Low alcohol
Light beer, low alcohol cider, session drinks
3 to 6%
Common beer range
Lager, pale ale, wheat beer, standard cider
6 to 10%
Strong beer or cider
IPA, Belgian styles, strong cider
10 to 15%
Wine range
Table wine, stronger mead, fruit wine
15%+
High strength fermentation
Dessert wine, specialty batches, fortified style bases
Fermentation guide
These notes help you collect better readings and understand the result without repeating the calculator output.
How fermentation produces alcohol
Yeast converts fermentable sugars into alcohol and carbon dioxide. As sugar decreases and alcohol increases, the measured gravity usually falls.
Improving measurement accuracy
Use a clean sample jar, avoid bubbles on the hydrometer stem, read at eye level, and apply temperature correction when the sample is not near calibration temperature.
Common brewing mistakes
Common issues include measuring before fermentation is complete, mixing up OG and FG, using uncorrected refractometer values, or taking a reading from a poorly mixed batch.
Hydrometer vs refractometer
A hydrometer directly measures density and is simple for final readings. A refractometer needs only a small sample, but alcohol correction is needed after fermentation begins.
Responsible brewing considerations
ABV helps with labeling, serving size awareness, and recipe tracking. Drink responsibly and avoid treating higher strength as a quality goal by itself.
Formula
ABV = (OG − FG) × 131.25
Variables
- OG = Original Gravity
- FG = Final Gravity
- 131.25 = standard approximation factor
Worked example
With OG 1.050 and FG 1.010, the gravity drop is 0.040. Multiply 0.040 by 131.25 to get 5.25% ABV.
Assumptions
The formula assumes typical brewing conditions and correctly measured gravity values.
Limitations
Results are estimates, not lab analysis. Temperature correction and instrument calibration can change the final value.
Frequently asked questions
Why is my ABV lower than expected?
Lower ABV can happen when original gravity is lower than planned, fermentation stops early, final gravity remains high, yeast health is weak, or temperature conditions slow fermentation.
Is this ABV formula accurate?
It is accurate enough for many homebrewing estimates when gravity readings are measured correctly. It is not a laboratory test, and very high gravity fermentations may need a more advanced formula.
Can I calculate ABV without a hydrometer?
You need a way to compare sugar density before and after fermentation. A hydrometer is the most common option. A refractometer can help, but readings after fermentation need alcohol correction.
Why do refractometer readings need correction?
Alcohol changes how refractometers read liquid after fermentation begins. Final gravity from a refractometer should be corrected before ABV is estimated.
Does temperature affect gravity readings?
Yes. Hydrometers are calibrated for a specific temperature, so warmer or colder samples can shift the reading. Use temperature correction when accuracy matters.
Can I use this for cider or wine?
Yes. This calculator can estimate ABV for beer, cider, wine, mead, and similar fermentation projects. For stronger batches, treat the result as a practical estimate.
What is apparent attenuation?
Apparent attenuation shows the percentage drop from original gravity points to final gravity points. It helps describe how much of the measured extract was fermented.
Is final gravity always lower than original gravity?
For a normal fermented drink, final gravity should be lower than original gravity. If it is not, check the readings, calibration, temperature, and whether fermentation started.
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