Jam Pectin Calculator

How it is calculated

Both amounts are percentages of the prepared fruit weight. sugar = fruit × sugar ratio / 100 and pectin = fruit × rate / 100, where the pectin rate depends on the fruit type you choose: low-pectin fruit 2%, medium 1%, high 0% (no added pectin). The batch total is fruit + sugar + pectin. Everything is in grams: pectin to 1 decimal, sugar and total rounded to whole grams. Fruit weight and sugar ratio must be above zero. The total is the weight of the raw ingredients, not the yield after cooking, because boiling drives off water. Pectin products differ in strength, so follow the packet if its dose is different.

Common mistakes

• Weighing the fruit with stones, stalks or peel on. Weigh the prepared fruit that actually goes in the pot, since the amounts are percentages of that weight.
• Entering the sugar as a number of grams. The field is a ratio in percent of the fruit weight, so 750 g of sugar for 1000 g of fruit is 75.
• Expecting the total to equal the jar yield. It is the raw weight; water boils off during cooking, so you will get less jam.
• Choosing a fruit pectin level by guess. Pick the group (low, medium or high) that matches your fruit, as a wrong choice changes the pectin dose by several grams.
• Using the pectin figure with a product that has its own dose. Commercial pectins vary in strength, so check the packet before adding.