Most tell you the measurements—8x8, 9x9 or 13x9—but there are other numbers down there, too, and they tell you some important things.

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Photo: Jennifer Causey; Styling: Missie Neville Crawford

If you’ve ever inherited (or purchased) some older casserole dishes, you know the hassle that can be figuring out exactly what size dishes you have on your hands.

You probably have noticed—and rely on—the fact many newer metal pans stamp a measurement in the bottom. On glass dishes, you may notice etched measurements in inches or centimeters, too.

Watch: How to Make Breakfast Sausage Casserole

Older dishes, however—and, truthfully, some newer ones—keep their capacity a bit of a mystery. They may have no size measurements, or they may have a collection of random numbers that you suspect may be speaking to you, but you long ago lost any deciphering codes.

Here, a few of the numbers you might find on the bottom of casserole dishes and what they mean:

### Pan Size

Rectangle and square dishes often sort by the two-dimensional measurements: 7x5, 8x8, 9x9, 13x9, and so on. A few will add the third dimension, height, which is great to know as that adds or removes a substantial capacity.

If you don’t see those measurements, you can always use a tape measure to measure from the inside walls of the dish. Surprise: older dishes may not meet typical standard dish sizes we use in recipes today.

### Dish Volume

Round dishes, and more unique casserole dish shapes, often measure in quarts, cups, and ounces, rather than inches. Less commonly, you’ll see a dish capacity number on square or rectangular dishes.

However, these numbers can be really helpful: If you, for example, see an 8-cup square pan, that’s likely an 8x8 pan. A 9x13 rectangle pan with two-inch sides can hold 16 cups. This helpful chart will guide you to proper dish volumes.

These numbers can come in handy if you ever have a recipe that calls for a two-quart dish but you don’t have a round two-quart dish. You know you can use an 8x8 or 9x9 pan.

### Unique Brand Numbers

Some brands have unique identifiers on their dishes, so if you’ve inherited stoneware, Dutch ovens, or other great cookware pieces, you may have a bit more help in identifying what you have.

For example, Emile Henry stamps all of their dishes with a product number or “shape code.” A 6121 is a nine-inch pie dish. A 0201 is a salt pig, which is ideal for keeping by your stove for quickly adding a touch of salt to dishes you’re making. A 9042 is a classic oval gratin dish.

Ever inherit a Le Creuset Dutch Oven and don’t know the capacity? You can measure with cups of water, pouring one at a time to gauge how much the pot can hold. Or you can also lift the lid and look for the stamped number.

A 24 is a 5.5-quart (4.2-liter) round dutch oven. A 25? That’s a 3.5-quart (3.2-liter) oval dutch oven. A 40 stamped inside the lid lets you know you’re holding (we suspect with great effort) a 15-quart (14.1-liter) oval dutch oven. That’s a big pot!

Stamped numbers are also visible on the bottom of Le Creuset skillets and grill pans. Flip them over, and you’ll be able to determine what size you’re holding. Braisers, shallow ovens, and sauciers all have this helpful stamp, too. Get a full breakdown of each number.

Staub uses stamped numbers to tell you about their products, too. A 28 on a round dutch oven means you’re holding a six-quart (6.7-liter) round cocotte. A 28 on a squat braiser signals it holds 3.25 quarts or 3.7 liters.

Staub uses this system on their round and oval Dutch ovens (they call them cocottes), braisers, and fish dish. This list can help you determine which Staub dishes you have.

Pyrex dishes also hide a little secret code: Many contain a three- or four-digit number that corresponds to a specific dish. A series of Mixing Bowls will feature 401 (1.5 pint), 402 (1.5 quart), 403 (2.5 quart), 404 (4 quart). The iconic two-quart green-and-white casserole dish is a 232. The eight-inch square glass dish you’ll likely buy today is a 2222. If you inherited a few pieces, this list can help you decipher older dishes.