The Rule of 86
The Rule of 86: how many gallons of sap it takes to make a gallon of syrup, and what your collection will yield.
In the app, on the Shack tabQuick Brix reference
| Sap °Brix | Ratio (Rule of 86) | Sap for 1 gal syrup |
|---|---|---|
| 1.5° | 57.6:1 | 57.6 gallons |
| 2.0° | 43.2:1 | 43.2 gallons |
| 2.5° | 34.6:1 | 34.6 gallons |
| 3.0° | 28.8:1 | 28.8 gallons |
How the Rule of 86 works
Maple sap is mostly water with a little sugar, usually around 2% (2°Brix). Finished syrup is about 66.9% sugar. The Rule of 86 is the shortcut sugarmakers have used for a century to bridge those two numbers: divide 86.4 by your sap's °Brix and you get the gallons of sap needed per gallon of syrup. Sweet sap from healthy, open-grown trees can run 3° and cut your boiling nearly in half; late-season or stressed trees can drop below 1.5° and double it.
The Jones Rule of 87 is the modern correction. When C.H. Jones worked out the original rule in the 1940s, syrup was finished at a slightly lower density than today's 66.9°Brix standard. UVM researchers revisited the math and found 87 fits the modern standard better. The difference is small, but if you sell in bulk, it's the honest number.
Measure your sap, don't guess
A $30 sap hydrometer or refractometer pays for itself the first week. Producers who assume "2 percent" often discover their bush runs 1.6°. That means 54 gallons per gallon of syrup, not 43, and every fuel and revenue estimate built on the guess is off by 25%.
Sources: UVM Proctor Maple Research Center; North American Maple Syrup Producers Manual.
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