Brix is a measurement of the amount of sugar in a solution per weight of total solution. A solution that is 10 degrees Brix has 10 g of sugar per 100 g of solution, or if the solution is simply sugar and water, there are 90 g of water and 10 g of sugar. Brix is often used in winemaking to determine potential alcohol content of a wine.
Put the hydrometer into the sugar solution. Depending on the hydrometer, it may measure Brix directly, or it may measure specific gravity of the solution.
Convert to Brix if the hydrometer has measured specific gravity by using the formula Brix = 261.3*(1 - 1/g), where g is the specific gravity
Measure the weight of a reference amount of the sugar solution now that the Brix degrees of the solution have been obtained. For example, if there are 5 L of solution, measure the weight of 100 mL by weighing an empty liquid measuring cup, then filling it with 100 mL of solution and weighing it again. Then, subtract the empty measure from the filled measure to get the weight of 100 mL of liquid.
Divide the total volume of the sugar solution by the reference amount (in the example, 100 mL) to get the number of reference amounts in the total volume. In the example, this is 5 L/100 mL = 50 reference amounts
Multiply the weight of one reference amount by the total number of reference amounts present to get the total weight of the sugar solution.
Divide the degrees Brix of the solution by 100, then multiply by the total weight of the sugar solution calculated in Step 5. The resulting number is the total weight of sugar in the solution.