Generally we recommend½ pint (8 oz or 1 cup) jars for low-sugar jams and jellies. The ¼ pint (4 oz or ½ cup) are a good size also if you’re making the jam or jelly for gifts.
You can use 1 pint (2 cup) jars but it’s important to remember that a jar of low-sugar jam or jelly will last only about 3 weeks in the refrigerator once opened. So unless you and your family can eat 2 cups of jam in 3 weeks, it’s better to use the smaller jars.
The processing time for all three jar sizes of jam or jelly is the same.