Honey Moisture Calculator
Turn a refractometer reading into honey moisture content and a clear answer on whether it's dry enough to bottle, sell, or store.
Moisture decides whether your honey keeps or ferments. Too wet and the yeasts already in the honey turn the sugars to alcohol. Dry enough and a sealed jar lasts for years. Enter your refractometer reading, either moisture % or °Brix, and this calculator tells you the water content and whether the honey is safe to bottle, sell, or store.
Calculator
Refractometer reading
Take the reading at room temperature on well-mixed honey, and average two or three drops. Honey varies from cell to cell.
17.5% moisture
Moisture
17.5%
Brix (approx.)
79.7°Bx
Good: Safe to bottle and sell
Up to 18.6% meets the US Grade A standard and resists fermentation under normal storage. Keep it sealed and out of humid air.
Where this falls
Assumptions & Notes
- Brix to moisture uses the International Honey Commission and AOAC refractive-index relationship, fit to moisture % = 91.63 - 0.9302 x Brix over the honey range.
- National standards (AOAC, ICUMSA, DIB) can differ by 1 to 2%. A dedicated honey refractometer that reads moisture directly is the most reliable.
- Risk bands follow US honey grading: 18.6% is the Grade A line, and about 20% is the practical sale limit.
- Always calibrate your refractometer and read at a stable temperature.
What the moisture number means
Ripe honey is roughly 17 to 18% water. The drier it is, the lower the chance of fermentation and the longer it keeps. The US Grade A standard caps moisture at 18.6%, and most buyers won't take honey for sale above about 20%, where fermentation becomes likely.
Below about 18.6%
Safe to bottle and sell. Keep jars sealed and away from humid air, since honey readily absorbs moisture.
Above about 18.6%
Use it soon, refrigerate or freeze it, dry it down, or save the wettest batches for mead.
Reading Brix on a non-honey refractometer
Many beekeepers own a general "sugar" or brewing refractometer that reads in °Brix. Because honey's sugars aren't pure sucrose, you can't just subtract Brix from 100 to get moisture. That overstates the water by a couple of points. This tool uses the refractive-index relationship from the International Honey Commission and AOAC reference tables, so a Brix reading converts to a realistic honey moisture figure. If you sell honey, a dedicated honey refractometer or a lab test is still worth it.
Sources: USDA United States Standards for Grades of Extracted Honey and the International Honey Commission Harmonised Methods (water content by refractive index).
Harvest tip
Frequently Asked Questions
What moisture level is safe for honey?
Below about 17% is excellent and stores indefinitely. Up to 18.6% is fine and meets the US Grade A standard. Between 18.6% and 20% the fermentation risk rises, so sell or eat it soon and store it cool. Above 20% honey is likely to ferment and is generally too wet to sell as honey.
My refractometer reads Brix, not moisture. How do I convert?
Honey moisture does not map to Brix by a simple "100 minus Brix". This calculator uses the refractive-index relationship from the International Honey Commission and AOAC tables, which across the normal honey range is close to moisture % = 91.63 - 0.9302 x Brix. Switch the input to °Brix and it converts for you. A dedicated honey refractometer that reads moisture directly is the most reliable.
Why does honey ferment?
Honey naturally contains osmotolerant (sugar-loving) yeasts. When moisture is high enough, those yeasts grow and ferment the sugars, producing alcohol and CO₂. The honey bubbles, smells boozy, and can blow lids. Keeping moisture below about 18% deprives the yeast of the water it needs.
How do I lower honey moisture?
Best is to leave frames on the hive until most cells are capped. After extraction you can dry honey with warm, moving air (a dehumidifier in a closed room with the honey in shallow open containers or in the extractor), or blend a wet batch with drier honey. Never overheat it, since that damages flavor and enzymes.
When should I harvest based on moisture?
A common rule of thumb is to harvest when frames are at least 80% capped, then confirm with a refractometer reading under ~18%. If it reads higher, leave it on the hive longer or dry it before bottling.