Refractometer Readings (°Brix)

Calibrated in % Sucrose. For reference, pure water reads 0° Brix.

Within a given species of plant, the crop with the higher refractive index will have higher sugar content, higher mineral content, higher protein content and a greater specific gravity or density.
This adds up to a sweeter, more densely nutritious food (maximum nutritional value) with lower nitrate and water content and better storage attributes.

Crops with higher Brix will produce more alcohol from fermented sugars and be more resistant to insects, thus resulting in decreased (or zero) insecticide usage. For insect resistance, maintain a Brix of 12 or higher in the juice of the leaves of most plants. Crops with higher solids content will have a lower freezing point and therefore be less prone to frost damage. (See “Tomatoes Survive Freeze “.)

This reading can also indicate soil fertility needs. If soil nutrients are in the best balance and are made available (by microbes) upon demand by plants, readings will be higher.

Refractometers are easy to use. To make a reading, place 2 or 3 drops of the liquid sample on the prism surface, close the cover and point toward any light source. Focus the eyepiece by turning the ring to the right or left. Locate the point on the graduated scale (0 – 32) where the light and dark fields meet. Read the % sucrose (solids content) on the scale.


Peaches: 6-Poor 10-Average 14-Good 18- Excellent 28-Superior

Apples: 6-Poor 10-Average 14-Good 18- Excellent 28-Superior

Strawberries: 6-Poor 10-Average 14-Good 16- Excellent 24-Superior

Sweet corn: 6-Poor 10-Average 18-Good 24-Excellent 36-Superior