I've actually have done the experiment of Hydrometer readings to Refractometer readings using table sugar and room temp tap water. I also plotted it in graph form for my own personal use. Here's a few point from the chart SG Refractometer SG/Ref 1.006 2.0 3.00 1.023 6.6 3.48 1.044 11.8 3.73 1.072 18.7 3.85 1.90 23 3.91 1.105 26.4 3.98 (pretty close to 4) This shows that the refractometers are not that accurate in the lower gravity readings but fairly close for typical wine readings. JL