Honey Moisture Content Calculator

Why honey moisture matters

Honey’s water content is one of the biggest factors affecting shelf stability. When moisture is too high, yeasts can ferment the sugars, creating off-flavors, gas pressure in sealed containers, and product loss. Many beekeepers target a moisture range that is broadly considered stable for storage (often cited around 18–19% water or lower), while recognizing that risk also depends on yeast load, storage temperature, and handling.

What this calculator does

This tool converts a refractometer degrees Brix (°Bx) reading into an estimated honey moisture percentage. Refractometers measure refractive index; the °Bx scale is a practical way of expressing dissolved solids (roughly “sugar concentration”) in many foods. In honey, higher °Bx generally corresponds to lower water content.

Formulas used (°Bx to moisture)

Within typical honey ranges, a simple approximation can be used:

Where:

• B = refractometer reading in °Bx
• M = estimated moisture (%)

This is a rule-of-thumb conversion intended for quick checks. Commercial operations often use calibrated honey refractometers and standard moisture tables; those methods can be more accurate than a single linear equation.

How to read a refractometer (quick workflow)

1. Calibrate your refractometer per the manufacturer’s instructions (commonly with distilled water or a calibration solution).
2. Sample honey from the frame/super (ideally well-mixed if taken from extracted honey).
3. Apply a thin film on the prism, close the cover plate, and wait briefly for temperature equilibration.
4. Read the boundary line and record °Bx.
5. Enter the °Bx value here to estimate moisture (%) and compare to your target threshold.

Interpreting your result

• Lower moisture (higher °Bx): generally safer for long-term storage and less fermentation risk.
• Higher moisture (lower °Bx): increased fermentation risk—especially if honey will be stored warm or sealed for long periods.

Use the estimate as a decision aid: if you’re near a cutoff, take multiple readings (different frames/areas) and consider confirming with a honey moisture reference table or a honey-scale refractometer.

Worked example

Suppose your refractometer reads 80.0 °Bx.

Using the equation:

• M = 78 − 0.75 × 80
• M = 78 − 60 = 18.0%

At ~18% moisture, many beekeepers consider the honey broadly stable, assuming proper storage and reasonable yeast levels. If your value were closer to 19–20% or higher, you might delay harvest, increase ventilation/dehumidification (with care), or keep supers on longer to allow further drying and capping.

Quick comparison table

Limitations & assumptions

• Approximation: The conversion here is a simplified linear rule; real °Bx-to-moisture relationships can be non-linear and are often handled via standard tables.
• Instrument scale: Some “honey refractometers” read moisture directly rather than °Bx. Do not enter a moisture-scale reading as °Bx.
• Temperature effects: Readings can vary with sample and instrument temperature. Automatic temperature compensation (ATC) helps, but doesn’t eliminate all error—follow your device guidance.
• Calibration & cleanliness: Small errors from an uncalibrated refractometer, residue on the prism, or bubbles can shift results.
• Sampling variability: Moisture can vary between frames and within a super; take multiple readings if you’re making a harvest decision.
• Food safety/storage context: Fermentation risk depends on more than moisture (yeast load, storage temperature, headspace, handling). Treat this as guidance, not a guarantee.

References (for further reading)

• Refractometer manufacturer instructions for calibration, ATC behavior, and correct scale usage.
• Beekeeping association/extension resources on honey moisture targets and fermentation risk (often include standard moisture tables).