The calculator is intended for professional refractometers. It is not suitable for instruments with ATC (automatic temperature compensation). For handheld instruments without ATC its usability is limited, because the measuring range for temperatures above 20°C / 68°F would have to be extended downwards (i.e. just below the value of water at 20°C / 68°F), which is normally not the case for handheld instruments. In addition, the reading accuracy of these devices is usually too low for such fine adjustments.
Depending on the temperature, the calculator returns the refractive index of pure water and then uses this to calculate the values of the other common units of measurement of the refractometers we commonly use. These are the values that a properly adjusted refractometer must display at the temperature entered when measuring water.
Since almost no one has an absolutely accurate indicating thermometer, an additional "thermometer error" can be specified. This can be determined with the help of the Thermometer error calculator. The temperature entered here is then the temperature displayed on this thermometer, not the real one.

General Information about Refractometers