ABV Calculator
Get alcohol by volume from original and final gravity, in SG, Plato or Brix, with the standard and high-gravity formulas, ABW and calories per 12 oz.
ABV Calculator: with the default inputs, alcohol by volume is 5.25%.
Hydrometer readings. Brix is treated as equal to Plato, which holds within about 0.1° at wort strengths.
Before fermentation, after pitching.
When fermentation has finished — the same reading on two or three days running.
- ABV by the other formula
- 5.34%
- Alcohol by weight
- 4.11%
- Apparent attenuation
Share of the original gravity points the yeast consumed.
- 80%
- Calories per 12 oz (355 mL)
- 162
- Carbohydrate per 12 oz
Grams, from the real extract left in the beer.
- 15.2
- OG as specific gravity
- 1.05
- FG as specific gravity
- 1.01
Assumptions
- Readings are hydrometer readings corrected to the hydrometer's calibration temperature.
- Brix is treated as equal to Plato. A refractometer final reading must be alcohol-corrected first.
- ABW = 0.79 × ABV ÷ FG, using 0.79 g/mL for ethanol.
- Calories follow the ASBC method with an ash allowance of 0.1°P; they are an estimate, not a lab analysis.
| Apparent attenuation | FG (SG) | ABV, standard | ABV, alternate |
|---|---|---|---|
| 60% | 1.02 | 3.94% | 4.04% |
| 65% | 1.018 | 4.27% | 4.37% |
| 70% | 1.015 | 4.59% | 4.7% |
| 75% | 1.013 | 4.92% | 5.02% |
| 80% | 1.01 | 5.25% | 5.34% |
| 85% | 1.008 | 5.58% | 5.66% |
Most ale yeasts reach 65–80% apparent attenuation; lagers and dry strains go higher.
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How this is worked out
The formula
Standard: ABV = (OG − FG) × 131.25 Alternate: ABV = 76.08 × (OG − FG) ÷ (1.775 − OG) × (FG ÷ 0.794) ABW = 0.79 × ABV ÷ FG Plato → SG: SG = 1 + P ÷ (258.6 − (P ÷ 258.2) × 227.1) Calories per 12 oz = (6.9 × ABW + 4.0 × (RE − 0.1)) × FG × 3.55 RE (real extract, °P) = 0.1808 × OE + 0.8192 × AE OG, FG = original and final specific gravity; OE, AE = the same in °Plato
Open How it’s calculated above to see this worked through with your own numbers.
What you enter
- Reading scale
- Hydrometer readings. Brix is treated as equal to Plato, which holds within about 0.1° at wort strengths.Specific gravity (1.050) · Degrees Plato (°P) · Degrees Brix (°Bx)
- Original gravity (OG)
- Before fermentation, after pitching.from 0 to 50 · defaults to 1.05
- Final gravity (FG)
- When fermentation has finished — the same reading on two or three days running.from 0 to 50 · defaults to 1.01
- Formula
- Choose one of 2 options.Standard: (OG − FG) × 131.25 · Alternate (more accurate for strong beers)
What you get back
- Alcohol by volumemain answer
- ABV by the other formula
- Alcohol by weight
- Apparent attenuation
- Share of the original gravity points the yeast consumed.
- Calories per 12 oz (355 mL)
- Carbohydrate per 12 oz
- Grams, from the real extract left in the beer.
- OG as specific gravity
- FG as specific gravity
What this assumes
- Readings are hydrometer readings corrected to the hydrometer's calibration temperature.
- Brix is treated as equal to Plato. A refractometer final reading must be alcohol-corrected first.
- ABW = 0.79 × ABV ÷ FG, using 0.79 g/mL for ethanol.
- Calories follow the ASBC method with an ash allowance of 0.1°P; they are an estimate, not a lab analysis.
About this calculator
Yeast turns sugar into alcohol and carbon dioxide, and because alcohol is lighter than water and sugar is heavier, the density of the liquid falls as it ferments. Measure the density before fermentation (original gravity, OG) and after (final gravity, FG), and the drop tells you how much alcohol was made. That is all an ABV calculator does — but which formula you use, and how you read the hydrometer, both matter.
How to calculate ABV
The everyday homebrew formula is ABV = (OG − FG) × 131.25. A beer that starts at 1.050 and finishes at 1.010 is (0.040) × 131.25 = 5.25%. It is quick and accurate enough for most beers up to about 6–7%.
The alternate formula, 76.08 × (OG − FG) ÷ (1.775 − OG) × (FG ÷ 0.794), accounts for the fact that the relationship is not quite linear: at high gravities the simple formula under-reads. For the same 1.050 → 1.010 beer it gives 5.34%; for a 1.100 barleywine finishing at 1.025 the gap is closer to a full point. Use it for imperial stouts, barleywines, meads and wines.
How to use it
Choose how you took the readings — specific gravity (1.050), degrees Plato or Brix — and enter OG and FG. Plato and Brix are converted to specific gravity first. Then pick the formula; the other one is always shown for comparison. Correct each hydrometer reading for temperature before entering it.
Reading the results
- ABV is what goes on a label.
- ABW (alcohol by weight) is lower, because ethanol weighs about 0.79 g per mL. A few US states historically regulated beer by weight.
- Apparent attenuation is the share of gravity points the yeast consumed — a quick check on whether fermentation finished.
- Calories and carbs per 12 oz use the American Society of Brewing Chemists method: alcohol at 6.9 kcal per gram plus the remaining extract at 4 kcal per gram.
The chart puts your OG across the bottom and FG up the side, with bands for each strength, so you can see what a couple of extra points of attenuation would add. The table shows the ABV your OG would give across the usual range of attenuation.
Caveats
A refractometer reading after fermentation is distorted by alcohol and reads high, so it cannot go straight into this calculator as an FG; only a hydrometer FG can. All of these formulas are empirical fits for beer-strength worts, so very strong ferments are approximate. For a legal label, have the alcohol measured by a lab.
Frequently asked questions
▸How do you calculate ABV from gravity?
Subtract the final gravity from the original gravity and multiply by 131.25. An OG of 1.050 and FG of 1.010 gives 0.040 × 131.25 = 5.25% ABV.
▸Which ABV formula is more accurate?
The alternate formula, 76.08 × (OG − FG) ÷ (1.775 − OG) × (FG ÷ 0.794), tracks measured alcohol better for strong beers. Below about 6% ABV the two differ by only a tenth of a point or so.
▸Can I use a refractometer for final gravity?
Not directly. Alcohol bends light differently from sugar, so a refractometer reads too high once fermentation starts. Use a hydrometer for FG, or apply a refractometer correction first.
▸What is the difference between ABV and ABW?
ABV is the volume of alcohol per volume of drink; ABW is its weight per weight. Because ethanol is lighter than water, ABW is about 0.79 × ABV ÷ FG — roughly four-fifths of the ABV.
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