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Alcohol by Volume (ABV) Calculator

See how much alcohol is in your homebrewed beer, cider or wine from its starting and final gravity readings, plus how much sugar the yeast used.

Level: Grade 6

  • Common Core standard 6.EE.A.2.cEvaluate expressions at specific values of their variables. Include expressions that arise from formulas used in real-world problems. Perform arithmetic operations, including those involving whole-number exponents, in the conventional order when there are no parentheses to specify a particular order (Order of Operations).
  • Common Core standard 6.NS.B.3Fluently add, subtract, multiply, and divide multi-digit decimals using the standard algorithm for each operation.
Printable worksheet

Alcohol by Volume (ABV) Calculator

Know the answer you need? Pick an input to work backward.

Inputs

How heavy the liquid is compared with water, before fermentation. For example, 1.050.

How heavy the liquid is compared with water, once fermentation has finished. For example, 1.010.

Formula

Result

Alcohol by volume

5.25%

From 1.05 to 1.01, the estimated alcohol content is 5.25% ABV.

Apparent attenuation
80%
Alternate formula gives
5.34%
Gravity points dropped
401 point is 0.001 of gravity

See the step-by-step solution ↓

Step-by-step solution

  1. Subtract the final gravity from the original gravity. The size of this drop shows how much sugar became alcohol

    1.05−1.01=0.04

  2. Multiply the drop by 131.25, the standard number that turns a gravity drop into percent alcohol

    0.04×131.25=5.25%

  3. Divide the drop by how far the start was above water (OG − 1), then multiply by 100. This shows what share of the sugar the yeast used

    0.041.05−1×100=80%

Test yourself

20 quick questions built from this calculator's formula: work out results, predict what happens when an input changes, and work backward from an answer. Every answer comes with the working.

What this calculator does

Find out how strong your homebrewed beer, cider or wine is, using two readings you take yourself. Yeast turns sugar into alcohol and carbon dioxide gas. Sugar makes a liquid heavier than water, and alcohol makes it lighter. So as the brew ferments, its specific gravity (how heavy it is compared with water) falls. You measure it with a hydrometer, a floating glass gauge, or with a refractometer.

The reading before fermentation is the original gravity (OG). The reading at the end is the final gravity (FG). Comparing the two gives a good estimate of how much alcohol the yeast made.

The calculator uses the popular homebrewing estimate ABV ≈ (OG − FG) × 131.25. You can also pick an alternate formula that stays closer at higher strengths. It also shows apparent attenuation: the share of the starting gravity points the yeast used up. That tells you whether fermentation finished where you expected.

Where it's used

Why this math matters outside the classroom:

  • Gravity readings. A beer that starts at 1.050 and finishes at 1.010 is about (1.050 − 1.010) × 131.25, which is 5.25% ABV.
  • Apparent attenuation. The same readings give an apparent attenuation of 0.040 ÷ 0.050, which is 80%.
  • Bottle labels. Homebrewers write an estimated ABV on bottle labels after taking a final hydrometer reading.
  • Cider and wine. Cider makers and home winemakers compare readings over several days to see when fermentation has finished.
  • Chemistry class. Chemistry classes use hydrometer readings to connect a falling density with sugar turning into alcohol.

Grade level and standards: Grade 6; Common Core State Standards for Mathematics 6.EE.A.2.c, 6.NS.B.3. © Copyright 2010. National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved.

How to use it

  1. Enter the original gravity you measured before adding the yeast, such as 1.050.
  2. Enter the final gravity once readings have stayed the same for a few days, such as 1.010.
  3. Choose the standard or alternate formula. The other formula's answer is shown next to it so you can compare.

What the inputs mean

Original gravity (OG)
Specific gravity compared with water, which reads 1.000. Most beers start between 1.035 and 1.080. Wines and meads often start at 1.080–1.120.
Final gravity (FG)
Most beers finish between 1.005 and 1.020. Dry wines and ciders can finish below 1.000, because alcohol is lighter than water.
Formula
The standard formula is short and close for typical beers. The alternate formula allows for alcohol being lighter than water. It usually reads a little higher, and the gap grows for strong brews.

Formula and method

ABV (standard) = (OG − FG) × 131.25
ABV (alternate) = 76.08 × (OG − FG) ÷ (1.775 − OG) × FG ÷ 0.794
Apparent attenuation = (OG − FG) ÷ (OG − 1) × 100

ABV means alcohol by volume: the percent of the drink that is alcohol. OG is the original gravity and FG is the final gravity, so OG − FG is how far the gravity dropped. Both formulas estimate alcohol from that drop.

The number 131.25 turns a gravity drop into a percent of alcohol for beers of typical strength. The alternate formula adds two corrections. One is for how much sugar you started with. The other is for alcohol's density (how heavy it is) of about 0.794 g/mL.

Attenuation is called apparent because alcohol pulls the reading lower than the leftover sugar alone would. So the true attenuation is lower than the apparent one.

Worked example

A pale ale started at 1.050 and finished at 1.010.

  1. Gravity drop: 1.050 − 1.010 = 0.040.
  2. Standard ABV: 0.040 × 131.25 = 5.25%.
  3. Apparent attenuation: 0.040 ÷ 0.050 × 100 = 80%.
  4. To compare, the alternate formula gives 76.08 × 0.040 ÷ 0.725 × 1.010 ÷ 0.794 ≈ 5.34%.

Result: The beer is about 5.25% ABV by the standard formula (about 5.34% by the alternate), with 80% apparent attenuation.

Understanding the result

Most ale yeasts reach roughly 70–80% apparent attenuation. A much lower number can mean fermentation stalled, or the brew has a lot of sugar yeast can't eat. A much higher number points to a very dry finish.

Attenuation above 100% can happen when the final gravity falls below 1.000. That's common with wine, cider and very dry beers.

Assumptions and limitations

  • Your readings are specific gravity, corrected to the temperature your hydrometer is set for.
  • If you used a refractometer after fermentation started, you corrected the reading for alcohol before entering it.
  • No sugar was added after the original gravity reading. Priming sugar added at bottling raises the alcohol by roughly a few tenths of a percent.
  • Both results are estimates. Lab tests measure alcohol directly and can differ by a few tenths of a percent.
  • The standard formula tends to read low for strong beers above about 8% ABV.
  • This calculator doesn't take degrees Plato or Brix (other sugar scales). Convert those to specific gravity first.

Frequently asked questions

Which ABV formula should I use?

For everyday beers, both give nearly the same answer, so the short standard formula is fine. For strong beers, barleywines and meads, the alternate formula is generally thought to be closer.

Can I measure ABV with only the final gravity?

Not reliably. The alcohol estimate comes from how far the gravity dropped, so you need the starting reading too. Recipe software can predict an original gravity, but a measured one is far better.

Why is my final gravity below 1.000?

Alcohol is lighter than water. Once almost all the sugar is gone, the alcohol pulls the reading below 1.000. It's common in wine, cider and mead.

Why does the temperature of a hydrometer reading matter?

Liquids expand as they warm, which lowers the reading. Most hydrometers are set for 60 °F (15.6 °C) or 68 °F (20 °C). Take your reading at that temperature, or use the correction chart that came with your hydrometer.

How this calculator is checked

Method: Common homebrewing estimates: ABV ≈ (OG − FG) × 131.25, and the alternate 76.08 × (OG − FG) ÷ (1.775 − OG) × FG ÷ 0.794; apparent attenuation by definition. The calculation is covered by automated tests with known reference values and edge cases. Last updated 2026-10-18. Found a problem? Tell us.

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