When cooking a soup or a main dish that includes a hearty sauce, your recipe may call for a canned amount of a certain ingredient. Although most modern recipes will include the measurement as well (ex: 1 can tomato paste/15 ounces) older recipes may just give you a can size and little else. This is particularly tricky if you're making grandma's traditional recipe for the first time and aren't sure how much of an ingredient should be included.
To find out how many cups in a can are required, it's useful to have a little history on the canning industry. According to the guide book "Canning and How to Use Canned Foods," by the National Canners Association (yes it was a real organization; it's now called the Food Products Association and yes the book is available on Amazon), while there are (or were) some can sizes considered standard, these measurements aren't based on any unit of volume or other requirements, and may lead to confusion for home cooks.
The Canners Association explained that in assigning the mysterious numbers to cans, the American can industry describes the dimensions of cylindrical cans by two numbers: diameter and height.
The guide book's authors lamented the lack of foresight by the canning industry:
The regular No. 2 can is too large for peas, corn, and beans in amount for the average family to use at one time, and the unused part is not as attractive when reheated. The No. 3 can of tomatoes is likewise an anomaly though the objection is not so strong as for the No. 2. The No. 2½ can was introduced as a compromise on the No. 3, especially for fruits, but recently a better size is being used having the diameter of the No. 2½ but only half the height. After machines have once been built to make and close cans of a certain size, it is difficult to make changes no matter how desirable it may be.
Again, most recipes in the 21st century won't require chefs to ascertain what amount of condensed milk (or evaporated milk, if you prefer) should go in their pumpkin pie recipe based solely on the can size. But in the event you run across a recipe that doesn't have the measurements spelled out, this handy chart can help guide you, both for how much to use and how much to buy of that pesky canned ingredient.
|8 ounces||8 ounces||1 cup|
|Picnic||10 1/2 to 12 ounces||1 1/4 cups|
|12 ounces vacuum||12 ounces||1 1/2 cups|
|No. 1||11 ounces||1 1/3 cup|
|No. 1 tall||16 ounces||2 cups|
|No. 1 square||16 ounces||2 cups|
|No. 2||1 pound 4 ounces or |
1 pint 2 fluid ounces
|2 1/2 cups|
|No. 2 1/2||1 pound 13 ounces||3 1/2 cups|
|No. 2-1/2 square||31 ounces||scant 4 cups|
|No. 3||4 cups|
|No. 3 squat||2 3/4 cups|
|No. 5||7 1/3 cups|
|No. 10||12 cups|
|No. 300||14 to 16 ounces||1 3/4 cups|
|No. 303||16 to 17 ounces||2 cups|
|Baby food jar||3 1/2 to 8 ounces||depends on size|
|Condensed milk||15 ounces||1 1/3 cups|
|Evaporated milk||6 ounces||2/3 cup|
|Evaporated milk||14 1/2 ounces||1 2/3 cups|
|Frozen juice concentrate||6 ounces||3/4 cup|
One last thing to note: Don't confuse cans with jars. Many people who preserve their own fruits and vegetables refer to this process as "canning," when in fact they're actually putting the preserves in jars. The verb "jarring" obviously has another meaning entirely.