Refractometer Calculator

✓ Reviewed by David Chen, Sc.B. | Technical Specialist

This professional-grade refractometer calculator helps brewers and winemakers convert Brix readings from a refractometer into Specific Gravity (SG) while applying the necessary Wort Correction Factor (WRI) for precise measurements.

Refractometer Calculator

The reading directly from your refractometer scale.

Standard is 1.04 for most wort. Use 1.00 for pure sugar water.

Refractometer Calculator Formula:

The conversion from Brix to Specific Gravity (SG) using the ASBC polynomial:

SG = 1 + (Brix / (258.6 - ((Brix / 258.2) * 227.1)))

Source: American Society of Brewing Chemists (ASBC)

Variables:

• Brix Reading: The refractive index measurement of the liquid’s sugar content.
• Wort Correction Factor (WRI): A ratio used to adjust for non-sugar components in wort that affect light refraction.
• Specific Gravity (SG): The density of the liquid relative to water (1.000).

Related Calculators:

• Alcohol by Volume (ABV) Calculator
• Hydrometer Temperature Adjustment
• Final Gravity (FG) Correction
• Yeast Pitch Rate Calculator

What is Refractometer Calculator?

A refractometer calculator is a digital tool used to translate the angle of light refraction in a liquid into a meaningful density measurement. While refractometers are highly convenient for small samples, they are calibrated for sucrose (pure sugar). In brewing, wort contains proteins and other solids that refract light differently, necessitating a “Correction Factor.”

This calculator applies the standard WRI (usually 1.04) and converts the resulting corrected Brix value into Specific Gravity, which is the standard unit used by most recipe designers and brewers to track fermentation progress.

How to Calculate Refractometer Values (Example):

1. Take a drop of your room-temperature wort and place it on the refractometer prism.
2. Read the Brix value (e.g., 13.0 °Bx).
3. Divide the Brix reading by your WRI (e.g., 13.0 / 1.04 = 12.5 Corrected Brix).
4. Apply the SG formula: $1 + (12.5 / (258.6 – ((12.5 / 258.2) * 227.1)))$.
5. The resulting Specific Gravity is approximately 1.050.

Frequently Asked Questions (FAQ):

Why do I need a Correction Factor (WRI)? Refractometers are calibrated for water and sucrose. Malt wort contains different compounds that bend light more or less than sucrose, making the raw reading slightly higher than reality.

Can I use a refractometer during fermentation? Not directly. Alcohol refracts light significantly differently than sugar. You must use a specialized “Refractometer Alcohol Correction” formula once yeast has started working.

Is a refractometer better than a hydrometer? It requires much less liquid (drops vs. a full jar) and is more durable, but it requires math or a calculator like this one to be accurate.

How do I find my specific WRI? You can find your specific WRI by measuring the same wort with both a calibrated hydrometer and your refractometer, then dividing the Brix reading by the Plato equivalent of the SG.