Last updated: October 2026
How to calculate ABV from original gravity and final gravity
Short answer: A beer with an original gravity of 1.050 and a final gravity of 1.010 is 5.25% ABV — just subtract the two readings and multiply the difference by 131.25 (0.040 × 131.25 = 5.25). The calculator above also shows a more accurate alternate formula (about 5.3%), apparent attenuation, and handles Brix, Plato, and temperature corrections.
The two ABV formulas
Standard formula: (OG − FG) × 131.25. This is the quick, widely used estimate — for example (1.050 − 1.010) × 131.25 = 5.25% ABV. It works well for typical beers under about 6% ABV.
Alternate formula: (76.08 × (OG − FG) / (1.775 − OG)) × (FG / 0.794). This more accurate version accounts for the fact that alcohol is lighter than water and changes the liquid's density as fermentation progresses. It stays reliable at higher gravities where the simple formula drifts. Most homebrewers use the standard number day to day and treat the alternate as a cross-check. Read more about what alcohol by volume actually measures.
Apparent attenuation — (OG − FG) / (OG − 1) × 100 — tells you what share of the sugars the yeast fermented. Our example beer attenuated 80%, right in the normal 70–85% range for ale yeast.
How to use the calculator
1. Enter your original gravity (OG) and final gravity (FG), each in Specific Gravity, Brix or Plato — mix units if you like (e.g. OG in Brix, FG in SG). 2. If the FG was read with a refractometer, tick the refractometer box so the calculator applies the Terrill correction — alcohol skews refractometer readings, and an uncorrected reading can throw the ABV off by a full percent. 3. If your hydrometer sample was warmer or colder than its calibration temperature, tick the temperature-correction box and enter the temperatures. 4. Read off both ABV formulas and the attenuation — results update live as you type.
Frequently asked questions
What is the difference between the standard and alternate ABV formulas?
The standard formula — (OG − FG) × 131.25 — is a simple linear estimate that works well for typical beers under about 6% ABV. The alternate formula — (76.08 × (OG − FG) / (1.775 − OG)) × (FG / 0.794) — accounts for the fact that alcohol is lighter than water and changes the liquid's density, so it stays more accurate at higher gravities. Use the standard number day to day and the alternate as a cross-check.
Do I need a hydrometer temperature correction?
Hydrometers are calibrated at a fixed temperature, usually 20°C (68°F). A warmer sample is less dense, so the hydrometer sinks lower and reads too low; a colder sample reads too high. If your sample was far from the calibration temperature — for example warm wort — tick the temperature-correction box and enter both temperatures. For room-temperature samples the difference is tiny, around 0.001 gravity points.
Brix vs Plato — what is the difference?
Both measure dissolved sugar as a percentage of the liquid's weight, and for homebrewing they are close enough to be interchangeable — this calculator converts them identically. Brix is the standard scale in the wine and juice world, Plato in the beer world. Just enter your refractometer reading in whichever scale it uses.
What is attenuation?
Apparent attenuation is the share of the original sugars the yeast fermented: (OG − FG) / (OG − 1) × 100. A beer with OG 1.050 finishing at 1.010 has 80% attenuation. Most ale yeasts attenuate 70–85% — a much lower number can signal a stalled fermentation.
Is my data private?
Completely. Every calculation runs locally in your browser with JavaScript — nothing you enter is sent to a server, stored, or tracked.
