Here are some general guidelines for the amount of fresh produce you'll need for each quart jar when canning...

Apples: 2-1/2 to 3 Pounds
Apricots: 1-1/2 to 2-1/2 Pounds
Asparagus: 2-1/2 to 4-1/2 Pounds
Beans: 1-1/2 to 2-1/2 Pounds
Beets: 3 Pounds
Berries: 1-1/2 to 2-1/2 Pounds
Carrots: 1 Pound
Cherries: 2 to 3 Pounds
Corn: 4 to 5 Pounds
Nectarines: 2 to 3 Pounds
Peaches: 2 to 3 Pounds
Pears: 2 to 3 Pounds
Plums: 1-1/2 to 2-1/2 Pounds
Rhubarb: 1 to 2 Pounds
Tomatoes: 2-1/2 to 3-1/2 Pounds