Original Gravity Calculator

In beer brewing, Original Gravity (OG) is one of the most important measurements. It represents the density of unfermented wort compared to water. OG tells brewers how much sugar is present in the wort before fermentation begins, which directly impacts the alcohol by volume (ABV) and final beer quality.

Original Gravity (OG) Calculator

OG = 1 + (Total Gravity Points ÷ (Batch Size × 1000))

How to Use the Original Gravity Calculator

Using an OG calculator is simple. You will need:

  1. Wort Specific Gravity – Measured using a hydrometer or refractometer.
  2. Temperature of Wort – Since density changes with temperature, you’ll need to correct the reading.

Steps to Use:

  1. Measure the gravity of the cooled wort (usually between 60°F to 80°F).
  2. Input the measured gravity value into the calculator.
  3. Enter the temperature of the wort.
  4. The calculator will correct for temperature and give the accurate Original Gravity.

Formula for Original Gravity

The OG correction formula (for hydrometer readings) is:

OG = Measured Gravity + Temperature Correction

Where:

Temperature Correction ≈ (Measured Temperature – Calibration Temperature) × 0.0003

Example:
If you measure a wort gravity of 1.048 at 75°F using a hydrometer calibrated at 60°F:

  • Temperature Difference = 75 – 60 = 15°F
  • Temperature Correction = 15 × 0.0003 = 0.0045
  • OG = 1.048 + 0.0045 = 1.0525 (rounded to 1.053)

Example Calculations

Example 1:

  • Measured Gravity: 1.062
  • Wort Temperature: 70°F
  • Hydrometer Calibration Temp: 60°F
  • Temp Difference = 10°F
  • Correction = 10 × 0.0003 = 0.003
  • OG = 1.062 + 0.003 = 1.065

Example 2:

  • Measured Gravity: 1.050
  • Wort Temperature: 60°F
  • Hydrometer Calibration Temp: 60°F
  • Temp Difference = 0°F
  • Correction = 0 × 0.0003 = 0
  • OG = 1.050

Why Original Gravity Matters in Brewing

  1. Predicting Alcohol Content
    OG, combined with Final Gravity (FG), determines ABV.
    ABV Formula: ABV (%) = (OG – FG) × 131.25
  2. Recipe Consistency
    Measuring OG ensures every batch meets the recipe specifications.
  3. Fermentation Monitoring
    Comparing OG and FG readings shows fermentation completeness.
  4. Troubleshooting Brewing Issues
    Low OG could mean incomplete mashing, while high OG might require dilution.

Tips for Accurate OG Measurement

  • Cool wort before measurement – Hot wort skews gravity readings.
  • Stir well before sampling – Avoid layered sugar concentrations.
  • Calibrate your hydrometer or refractometer regularly.
  • Avoid bubbles when taking readings.

Brewing Stages Where OG is Important

  1. After the Mash – Determines sugar extraction efficiency.
  2. Before Boiling – Helps decide if more malt or water adjustments are needed.
  3. After Boiling – The final OG reading before fermentation.

Relation Between OG, FG, and ABV

To calculate ABV, you’ll need both OG and FG:

Example:

  • OG = 1.060
  • FG = 1.015
  • ABV = (1.060 – 1.015) × 131.25
  • ABV = 0.045 × 131.25 = 5.91%

Common OG Ranges by Beer Style

Beer StyleTypical OG Range
Light Lager1.028 – 1.040
Pale Ale1.045 – 1.060
IPA1.055 – 1.075
Stout1.050 – 1.075
Barleywine1.080 – 1.120

Additional Brewing Insights

  • Higher OG generally results in stronger beer but also increases sweetness.
  • OG also influences mouthfeel and body.
  • Yeast strain choice affects how much sugar is fermented into alcohol.

20 FAQs About Original Gravity Calculator

  1. What is original gravity?
    It’s the measurement of sugar content in wort before fermentation.
  2. How do I measure OG?
    Using a hydrometer or refractometer.
  3. Why correct for temperature?
    Because density changes with temperature, affecting readings.
  4. Can OG predict ABV?
    Yes, with Final Gravity, you can calculate ABV.
  5. What is a good OG for beer?
    It depends on style—pale ales may be 1.045–1.060, stouts 1.050–1.075.
  6. Can OG be too high?
    Yes, it can stress yeast and cause incomplete fermentation.
  7. What if my OG is too low?
    Add more fermentable sugars or adjust the recipe.
  8. Is OG the same as specific gravity?
    OG is a specific gravity measured before fermentation.
  9. Do I need OG for cider or mead?
    Yes, it applies to any fermented beverage.
  10. Can refractometers measure OG?
    Yes, but they require correction for alcohol presence during fermentation.
  11. What is high gravity brewing?
    Brewing with an OG much higher than standard.
  12. What’s the relationship between OG and sweetness?
    Higher OG means more residual sweetness unless fermented dry.
  13. Can I estimate OG from malt bill?
    Yes, brewing software can predict OG from ingredients.
  14. Does OG affect carbonation?
    Indirectly, through sugar levels influencing yeast activity.
  15. Can OG readings be wrong?
    Yes, due to temperature errors, uncalibrated tools, or improper sampling.
  16. What is the typical hydrometer calibration temperature?
    Usually 60°F (15.6°C).
  17. Do I take OG after adding yeast?
    No, take it before pitching yeast.
  18. Why does OG vary by style?
    Different beer styles require different sugar concentrations.
  19. Can I convert Brix to OG?
    Yes, using conversion formulas.
  20. Is OG important for non-alcoholic beer?
    Yes, it still affects flavor and body.