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Refractometer

Convert Brix refractometer readings to specific gravity and correct for alcohol during fermentation.

The Refractometer tool converts Brix readings to specific gravity and corrects for alcohol presence during fermentation.

Convert Brix to SG, or calculate fermented SG based on OG and Brix reading

How to Use

Inputs

Input
Description

Fermented wort?

Checkbox -- enable this when measuring wort that has begun or completed fermentation

Original Gravity

Your OG before fermentation (only shown when "Fermented wort?" is checked)

Brix WRI

Your refractometer reading in Brix

Correction Factor

The wort correction factor (default 1.04)

Output

The tool displays the calculated Gravity (in SG or Plato, depending on your settings).

When Fermented wort? is checked, the tool additionally displays:

  • ABV (Alcohol by Volume) percentage

  • ABW (Alcohol by Weight) percentage

Pre-Fermentation (No Alcohol)

  1. Leave "Fermented wort?" unchecked

  2. Enter your Brix reading

  3. The tool converts directly to specific gravity

During/After Fermentation (With Alcohol)

  1. Check "Fermented wort?"

  2. Enter your Original Gravity

  3. Enter your current Brix refractometer reading

  4. The tool calculates the corrected gravity, ABV, and ABW

About Refractometers

Refractometers measure the refractive index of a liquid to determine sugar content. They require only a few drops of liquid, making them ideal for taking readings during the brewing process without wasting wort.

Advantages

  • Small sample size: Only 2-3 drops needed

  • Quick readings: Instant results

  • Temperature compensation: ATC (Automatic Temperature Compensation) models available

  • Durable: No fragile glass like hydrometers

  • Portable: Easy to carry and use

Limitations

  • Alcohol affects readings: Requires correction during/after fermentation

  • Calibration needed: Must be calibrated regularly

  • Learning curve: Reading scale takes practice

  • Not for FG alone: Need OG to calculate fermented readings

Types of Measurements

Pre-Fermentation (Wort Only)

Simple Brix to SG conversion when no alcohol is present:

  • Direct conversion using standard formula

  • Most accurate refractometer use case

  • No correction factor needed

During/After Fermentation

Complex calculation when alcohol is present:

  • Requires original gravity (OG) value

  • Uses correction formulas for alcohol

  • Less accurate than hydrometer for FG

Calibration and Correction

In-App Calibration Tool

The tool includes a built-in calibration feature to find your personal correction factor. Check the "Calibrate refractometer?" checkbox to reveal the calibration panel.

To calibrate:

  1. Take a sample of unfermented wort

  2. Read it with both your refractometer and a hydrometer

  3. Enter the Refractometer Reading (in Brix) into the calibration panel

  4. Enter the Hydrometer Reading (in SG or Plato, depending on your settings)

  5. The tool automatically calculates and applies the correction factor

The calculated correction factor is applied to the main Correction Factor field, so all subsequent readings will use your calibrated value.

Wort Correction Factor

Most refractometers are calibrated for sucrose (table sugar), but wort contains maltose and other sugars.

Typical Correction Factors:

  • 1.04: Most common default

  • 1.02-1.06: Typical range

  • Use the in-app calibration tool to determine yours experimentally

Finding Your Correction Factor Manually

  1. Measure same unfermented wort with both refractometer and hydrometer

  2. The correction factor is the Brix reading divided by the Plato equivalent of the hydrometer reading

  3. Repeat for multiple worts and average the results

Temperature Compensation

  • ATC Models: Automatic compensation 10-30°C (50-86°F)

  • Non-ATC: Must cool sample to 20°C (68°F)

  • Best Practice: Let sample reach room temperature

Common Calculations

Brix to Specific Gravity

Formula: SG = 1 + (Brix / (258.6 - (Brix * 0.88)))

Example Conversions

  • 10 Brix = 1.040 SG

  • 12 Brix = 1.048 SG

  • 15 Brix = 1.061 SG

  • 20 Brix = 1.083 SG

Alcohol Presence Correction

When alcohol is present, the refractometer reading is affected. The tool uses complex formulas to correct for this.

Best Practices

Taking Readings

  1. Clean the Plate

    • Use distilled water

    • Dry with soft cloth

    • No scratches or residue

  2. Sample Preparation

    • Mix wort thoroughly

    • Let sample settle

    • Avoid foam/bubbles

  3. Consistent Technique

    • Same light source

    • Same viewing angle

    • Multiple readings

Maintenance

  • Clean after each use

  • Store in case

  • Check calibration weekly

  • Avoid harsh chemicals

Comparing with Hydrometers

When to Use Refractometer

  • Pre-fermentation readings

  • Small sample volumes

  • Quick spot checks

  • Field measurements

When to Use Hydrometer

  • Final gravity determination

  • Most accurate FG

  • Large sample available

  • No calculations needed

Troubleshooting

Fuzzy/Unclear Reading

  • Clean the plates

  • Check for scratches

  • Adjust focus ring

  • Better light source

Inconsistent Readings

  • Temperature not stable

  • Calibration drift

  • Dirty optics

  • Sample not mixed

Doesn't Match Hydrometer

  • Check correction factor

  • Verify calibration

  • Account for temperature

  • Consider alcohol presence

Tips

  • Calibrate with distilled water regularly

  • Let samples reach room temperature

  • Clean and dry after each use

  • Use hydrometer for final gravity for best accuracy

Using with Brewfather

  • Convert Brix readings to SG for consistent record keeping

  • The tool remembers your last entered values

  • Use converted values when logging batch data

  • Track patterns across your brews for better predictions

Related docs

PreviousYeast Calculator
NextGravity Correction

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