How to Measure Gravity and Calculate ABV

Whether you’re brewing beer, making mead, or fermenting wine, understanding gravity readings is fundamental to tracking your fermentation and calculating alcohol content.

What is Specific Gravity?

Specific gravity (SG) measures the density of your liquid relative to pure water. Water has a specific gravity of 1.000. Sugar-rich wort or must reads higher — a typical beer OG might be 1.050, while a mead could start at 1.108.

Taking a Reading

1. Sanitize everything — your hydrometer, sampling tube, and hands.
2. Draw a sample — take enough to float the hydrometer freely.
3. Read at the meniscus — look at where the liquid meets the hydrometer stem at eye level.
4. Note the temperature — hydrometers are calibrated to a specific temperature (usually 60°F / 15.5°C).

Temperature Correction

If your sample is at a different temperature than your hydrometer’s calibration, the reading will be off. Our Gravity & ABV Calculator uses the standard polynomial correction to adjust for this:

• Hot liquids read lower than actual (hydrometer floats more)
• Cold liquids read higher than actual

As a rule of thumb, if you’re reading at 68°F with a 60°F hydrometer, you’re about 0.001 off — small, but it adds up for ABV calculations.

Calculating ABV

The simplest formula:

ABV = (OG − FG) × 131.25

For example, if OG = 1.050 and FG = 1.010:

ABV = (1.050 − 1.010) × 131.25 = 5.25%

For high-gravity brews (ABV > 9%), the alternate formula gives more accurate results:

ABV = (76.08 × (OG − FG)) / (1.775 − OG)

Our calculator automatically selects the best formula based on the estimated ABV.

Using the Free Calculator

Head to the Gravity & ABV Calculator to instantly calculate:

• ABV (simple and alternate formulas)
• Apparent attenuation
• Plato and gravity points
• Temperature-corrected FG
• Dilution/chaptalization calculations
• Estimated calories per 12oz serving

No sign-up required. When you’re ready to log readings over time and get automated reminders, start a free trial.

Key Takeaways

• Always record temperature with your gravity reading
• Use temperature correction for accurate ABV
• The simple formula works for most beers (under 9% ABV)
• For meads and high-gravity brews, the alternate formula is more accurate
• Track your readings over time to see fermentation curves — that’s where Levain comes in