Brix to Salinity Calculator
Brix refractometers read sugar, but they also respond to salt. If a Brix refractometer is what you own, here is the conversion to brine salinity - with its limits spelled out.
Results
Approximate conversion: %NaCl ≈ °Bx × 0.85. Acids and alcohol in active ferments distort readings - for critical batches use a salt-brine refractometer or titration.
Why the conversion is approximate
Salt and sugar raise refractive index by different amounts, and every ferment adds acids and alcohol that shift readings further. The 0.85 factor fits clean sodium chloride solutions at room temperature; in live ferments it is a ballpark check, not a measurement.
Quick reference
| °Bx reading | ≈ % NaCl |
|---|---|
| 2 | 1.7% |
| 5 | 4.3% |
| 10 | 8.5% |
| 15 | 12.8% |
| 20 | 17.0% |
Checking a brine by weight instead? The brine calculator computes salt for any water volume and percentage, and the vegetable salt ratio calculator covers dry-salted ferments like sauerkraut.
Frequently asked questions
Can I use a Brix refractometer to measure salt?
Approximately, yes. In a clean salt solution the salt concentration in percent is roughly the Brix reading times 0.85 - so a 10 °Bx reading indicates about 8.5% salt. It is a ballpark check, not a precision measurement.
Why is the Brix-to-salt conversion only approximate?
Refractometers respond to all dissolved solids. Salt and sugar bend light by different amounts, and live ferments add acids, alcohol and remaining sugars that skew the reading further. The 0.85 factor fits clean sodium chloride solutions at room temperature.
When is this conversion useful?
Quick sanity checks: confirming a mixed brine is roughly at target strength, or catching a badly wrong salt measurement before the batch goes in. For recipe-critical work, use a salt-specific refractometer, a brine hydrometer, or titration.
Does temperature affect the reading?
Yes. Refractometers with automatic temperature compensation handle small room-temperature swings, but hot or cold samples need correction. Let samples reach room temperature for the most reliable reading.