Refractometer calculator
Convert Brix to gravity before fermentation, and correct readings taken once alcohol is present. Leave the current Brix empty for a simple conversion.
Refractometer
Default wort correction factor: 1.04. Measure your own by comparing a refractometer and a hydrometer reading on the same wort.
How the correction works
Before fermentation, Brix converts to gravity with SG = 1 + Brix / (258.6 − Brix / 258.2 × 227.1), after dividing by the wort correction factor. Once fermentation starts, alcohol bends light differently and the refractometer reads high: the final gravity is estimated from the original and current Brix with Sean Terrill's cubic formula.
Questions
Why does my refractometer read high after fermentation?
Alcohol has a higher refractive index than water. Without correction, a finished beer can look several points sweeter than it is.
What is the wort correction factor?
Refractometers are calibrated with sucrose, and wort is not pure sucrose. The factor, usually 1.02–1.06, brings the reading in line with your hydrometer.
How accurate is the corrected FG?
Within a couple of points for most beers. For the final reading before bottling, a hydrometer remains the reference.
Track every batch, not just one number
Mashwerk computes this for every recipe and brew, from your own equipment and readings. Free plan, no credit card.
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