Example Data Table
| Batch |
Reading Type |
Original |
Final |
Temp |
Expected ABV |
| Pale Ale |
Hydrometer SG |
1.052 |
1.011 |
68 °F |
5.4% |
| Porter |
Hydrometer SG |
1.064 |
1.017 |
66 °F |
6.2% |
| Belgian Tripel |
Brix |
19.2 |
9.8 |
Automatic |
8.1% |
Formula Used
Specific gravity: SG = density of beer ÷ density of water.
Temperature correction: corrected SG = measured SG × water density factor at sample temperature ÷ water density factor at calibration temperature.
Brix to SG: SG = 1 + Brix ÷ (258.6 - ((Brix ÷ 258.2) × 227.1)).
Refractometer final SG: FG = 1.0000 - 0.00085683 × original Brix + 0.0034941 × final Brix.
Simple alcohol: ABV = (OG - FG) × 131.25.
Advanced alcohol: ABV = (76.08 × (OG - FG) ÷ (1.775 - OG)) × (FG ÷ 0.794).
Apparent attenuation: ((OG - FG) ÷ (OG - 1)) × 100.
Real extract: RE = 0.1808 × original Plato + 0.8192 × apparent Plato.
Calories: estimated from alcohol by weight, real extract, final gravity, and serving size.
How to Use This Calculator
Select the reading type first. Use hydrometer SG when your readings look like 1.050. Use Brix when your readings look like 12.5.
Enter original and final readings. Add sample temperatures and hydrometer calibration temperature when using SG mode.
Use the offset field if your hydrometer reads high or low in plain water. Enter the correction as gravity points.
For refractometer mode, enter a wort correction factor. Use your calibrated factor when available.
Add batch volume and serving size. Press calculate. Review the result above the form. Use CSV or PDF buttons for records.
Why Specific Gravity Matters
Specific gravity compares wort or beer density with water. Brewers use it to follow sugar changes during fermentation. A higher original gravity means more dissolved sugar. A lower final gravity shows that yeast converted sugar into alcohol and carbon dioxide. This calculator connects brewing practice with simple physics. Density, temperature, and dissolved solids all affect the reading.
Advanced Brewing Insights
Hydrometers are usually calibrated at one temperature. Warm samples read low because liquid expands. Cold samples read high. The tool corrects that shift when you enter sample and calibration temperatures. It also accepts refractometer Brix readings. Refractometers are useful before fermentation. After fermentation, alcohol bends light differently. That is why the final Brix correction uses both original and final readings.
What Results Mean
The result panel estimates corrected original gravity, corrected final gravity, gravity points, alcohol by volume, alcohol by weight, apparent attenuation, real attenuation, real extract, density, calories, and batch alcohol. These numbers help compare recipes. They also help diagnose slow fermentation. Low attenuation may indicate stressed yeast, high mash temperature, or unfermentable ingredients. Very high attenuation may suggest measurement error or contamination.
Better Measurement Practice
Take readings from a well mixed sample. Remove bubbles before reading a hydrometer. Spin the hydrometer gently, then read the bottom of the meniscus. Cool hot wort before measuring. Clean and calibrate instruments often. For refractometers, use a wort correction factor based on your own device. Record readings. Exported files keep the batch record consistent.
Reading Limits and Notes
Specific gravity is not a direct alcohol meter. It estimates alcohol from the density drop. Sugars, proteins, minerals, fruit, lactose, and spices can change the relationship. The calculator therefore shows several connected measures, not one final truth. Use them with tasting notes and process records.
Temperature control matters. A small gravity error can change the alcohol estimate. Measure near the calibration point when possible. If the sample is hot, cool it first. For strong beer, degas finished samples well. Carbonation can lift the hydrometer and cause a false reading.
Use density when comparing beer with water. Use Plato and extract values for recipe balance. Use attenuation when reviewing yeast performance. Together, these outputs give a clear view of fermentation progress.
FAQs
What is beer specific gravity?
Beer specific gravity compares beer or wort density with water. It shows how much dissolved material, mainly sugar, is present before and after fermentation.
What is original gravity?
Original gravity is the gravity reading before fermentation starts. It estimates the sugar available for yeast and helps predict possible alcohol strength.
What is final gravity?
Final gravity is the reading after fermentation slows or finishes. It shows remaining extract, dryness, and how much sugar yeast consumed.
Why does temperature correction matter?
Hydrometers are calibrated at a fixed temperature. Warmer or colder samples have different density behavior, so correction improves the reading.
Can I use refractometer readings after fermentation?
Yes, but final Brix needs correction. Alcohol changes refraction, so the calculator uses original and final Brix together.
What is apparent attenuation?
Apparent attenuation shows the percentage of gravity points consumed during fermentation. It is useful for judging yeast performance.
Why are simple and advanced ABV different?
The simple formula is fast and common. The advanced formula adjusts more for density and alcohol behavior, especially in stronger beers.
Are calorie results exact?
No. Calories are estimates based on alcohol and extract. Ingredients, residual sugars, and lab methods can change the true value.