What is the difference between net weight and drained weight on a package?

The net quantity on a package tells you what is inside excluding the packaging; on solid foods sold in a liquid medium there is a second statement as well: the drained weight. By the definition in the regulation, drained weight is the net quantity left after the liquid part has been removed by suitable methods. That is the one to use in working out a portion, because what goes onto the plate is what has been drained.

What do the two statements say?

Net quantity is the amount inside the package, excluding the packaging material and other materials packed together with the food. In a can of chickpeas that is the chickpeas and the brine together.

Drained weight shows only the solid part. If you see two numbers on the same can, that is why: one states the whole package, the other what is left in your hand after the strainer.

The difference between the two shows how much of the can is liquid. That difference changes with the product and the brand; there is no fixed ratio, which is why you have to read the second number on the can rather than guess.

The liquid medium here is the liquid used as an aid in preparing the food and having no decisive role at the point of purchase: water, salted water, brine, vinegar, sugar solutions or the fruit's and vegetable's own juice. In other words the liquid is not the product itself but its carrier.

Why are both printed on the label?

The labelling regulation requires the drained weight to be stated as well when a solid food is presented in a liquid medium. So the second number is not the manufacturer's choice but compulsory information.

The consequence is this: two cans of the same size may not contain the same amount of product. If two cans with equal net quantities have different drained weights, one has more liquid and the other more product, and that is only seen when the second number is read.

Which products show a large difference?

The difference is clearest in brined and canned products: olives, pickles, canned legumes, corn, tuna, fruit canned in syrup. In all of these part of the can is liquid.

The same distinction holds for products sold in brine such as cheese. In foods whose sauce is eaten together with the product, on the other hand, no such distinction is looked for; the distinction is set by whether the liquid is thrown away.

A difference can also appear between the glass jar and the tin can versions of the same product. In a jar the liquid is visible, so the ratio looks as though it can be guessed; in a can it cannot be seen without opening it, and the second number on the label is the only indicator.

Which one is used in working out a portion?

If you drain it before eating, the basis of your calculation is the drained weight. Taking the net quantity as the basis means counting the liquid you throw away into the amount you ate, and makes the can look bigger than it is.

The same number is used when working out how many portions the package holds. If you want to split a can in two, what gets split is the drained amount, not the large number on the can.

Recipes that use the liquid are the exception. If you add the canning liquid to the dish, the whole can is going onto the plate; then the calculation is done over the whole of it.

What can you do today?

When you open a can in the kitchen you can drain it and weigh it once; comparing it with the drained weight printed on the can shows how close that brand's label is. For products you buy often, that one-off measurement is useful every time afterward.

When deciding between two products on the shelf, looking at the drained weight rather than the large number is enough. If you also divide the price of both cans by that number, what each can actually gives you shows up at a glance.

Transferring the drained amount into a container after opening the can and writing it on top helps too; you then know how much is left, and at the next shop you do not have to guess which size will be enough.