Calculator Inputs
Example Data Table
| Beer Style | Observed OG | Observed FG | Volume | Target SG | PPG |
|---|---|---|---|---|---|
| Pale Ale | 1.052 | 1.011 | 5 gal | 1.058 | 46 |
| Porter | 1.064 | 1.018 | 19 L | 1.070 | 44 |
| Session IPA | 1.044 | 1.009 | 5.5 gal | 1.050 | 36 |
Formula Used
Temperature corrected gravity: corrected SG = observed SG × water factor at sample temperature ÷ water factor at calibration temperature.
Gravity points: points = (SG − 1) × 1000.
Simple ABV: ABV = (OG − FG) × 131.25.
Degrees Plato: °P = −616.868 + 1111.14SG − 630.272SG² + 135.997SG³.
Real extract: RE = 0.1808 × OE + 0.8192 × AE.
Advanced ABV: ABW = (OE − RE) ÷ (2.0665 − 0.010665 × OE). ABV = ABW × FG ÷ 0.794.
Sugar needed: pounds = needed points × gallons ÷ potential points.
How to Use This Calculator
Enter the observed original gravity and final gravity from your hydrometer. Add the sample temperature and the calibration temperature printed on the hydrometer. Choose the correct temperature unit. Enter batch volume, target gravity, sugar name, and potential points. Press calculate. The corrected gravity, ABV, extract, attenuation, gravity units, and sugar addition will appear above the form.
Brewing Specific Gravity Guide
Why Gravity Matters
Specific gravity shows how dense wort or beer is compared with water. Brewers use it to judge sugar strength before fermentation. They also use it after fermentation to estimate alcohol and yeast performance. A higher original gravity usually means more fermentable sugar. A lower final gravity usually means drier beer. This calculator joins both readings. It turns them into practical brewing numbers.
Correcting Hydrometer Readings
Hydrometers are calibrated at a set temperature. Many are calibrated at 60°F or 68°F. Warm wort is less dense than cool wort. That can make a reading look lower than reality. The calculator applies a temperature correction. It adjusts both original gravity and final gravity. This gives a stronger base for alcohol and attenuation estimates.
Alcohol and Extract Values
The simple ABV method is fast. It works well for most home brewing checks. The advanced method uses degrees Plato and real extract. It gives a deeper estimate for stronger beers. Original extract describes the sugar strength before fermentation. Apparent extract describes the final gravity reading. Real extract adjusts for alcohol effects in the finished beer.
Attenuation and Fermentation
Apparent attenuation tells how much gravity dropped during fermentation. It helps compare yeast strains and mash profiles. Real attenuation is usually lower. It accounts for alcohol density. Low attenuation may point to yeast stress, high mash temperature, or unfermentable sugars. Very high attenuation may show a dry finish or a measurement issue.
Planning Gravity Adjustments
The calculator also estimates sugar or extract needed to reach a target gravity. It uses batch volume and ingredient potential. Corn sugar is often near 46 points per pound per gallon. Dry malt extract is often near 44. Liquid malt extract is often near 36. Use your supplier value when available. This keeps additions realistic and repeatable.
Better Brewing Records
Good records improve every batch. Save the CSV file for spreadsheets. Save the PDF for brew day notes. Compare gravity, attenuation, and ABV across recipes. Small changes in mash temperature, yeast pitch, oxygen, and fermentation heat can change the result. Track those values with gravity readings. Your next recipe will be easier to tune.
FAQs
What is brewing specific gravity?
Brewing specific gravity compares wort or beer density with water. It mainly reflects dissolved sugars before fermentation and remaining extract after fermentation.
Why should I correct hydrometer temperature?
A hydrometer is calibrated for one temperature. Warm or cold samples shift density readings. Correction gives a more reliable gravity value.
What is original gravity?
Original gravity is the corrected gravity before fermentation starts. It estimates the sugar available for yeast to convert into alcohol and carbon dioxide.
What is final gravity?
Final gravity is the corrected gravity after fermentation finishes. It helps estimate dryness, residual sweetness, attenuation, and alcohol content.
Which ABV result should I use?
Use simple ABV for quick home brewing checks. Use advanced ABV when you want extract-based estimates for stronger or more detailed recipes.
What does apparent attenuation mean?
Apparent attenuation shows the percentage drop from original gravity to final gravity. It gives a simple view of fermentation progress.
What is PPG in brewing?
PPG means points per pound per gallon. It estimates how much gravity one pound of sugar or extract adds to one gallon.
Can this calculator replace lab testing?
No. It is best for brewing estimates and planning. Professional lab analysis is better for legal, commercial, or precise quality control work.