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Refractometers available for home use are typically calibrated to measure the amount of table sugar (sucrose) in a sample of water. The primary sugar in barley beer is maltose and not sucrose, so the readings made using a refractometer must be adjusted before use. This tool makes those adjustments to provide an accurate gravity reading from a given sample.

If this is your first time using a refractometer, I strongly suggest you read my article on refractometer use, and also take time to calibrate your refractometer before use.

Online Articles: Using a Refractometer for Beer Brewing

Using the Refractometer Tool

o	Select the Refractometer Tool from the Tools menu or ribbon.

o	If you have not already done so - please calibrate your refractometer using the "Calibrate Refractometer button and Refractometer Calibration Options

o	Select the calculation to perform (see below)

Calculating the Unfermented Wort Gravity

The unfermented wort gravity calculator is intended to be used before you have started fermentation - either to measure the gravity of wort in the boiler or mash or to measure the original gravity of your wort before you add yeast.

o	Select "Unfermented wort gravity" as the calculation

o	Enter the refractometer reading for the unfermented wort (at room temperature - cool the sample before measuring)

o	The corrected specific gravity will be displayed

Calculating the Gravity of Fermenting Wort

This calculation is used once fermentation has started or can also be used at the end of fermentation to get the final gravity. You need to have both the original gravity (taken before fermentation started) and a current refractometer reading to get an accurate gravity during fermentation.

o	Select "Fermenting wort gravity" as the calculation

o	Enter the refractometer reading for the fermenting wort (at room temperature - cool the sample before measuring)

o	Enter the original gravity reading - taken before fermentation was started

o	The corrected specific gravity will be displayed

Backing Out the Original Gravity of a Finished Beer

This calculation, though rarely used, can actually estimate the original gravity of the beer using a final gravity measurement taken with both a refractometer and hydrometer. It is useful if you forgot to measure the original gravity up front.

o	Select "Fermenting wort gravity" as the calculation

o	Enter the refractometer reading for the finished beer (at room temperature - cool the sample before measuring)

o	Enter the hydrometer reading for the finished beer

o	The estimated original gravity will be displayed under "Corrected gravity"