Start with servings per container

FDA's own instruction for reading any Nutrition Facts label is to look first at servings per container and the serving size, before calories and before anything else. On a frozen meal this one step prevents most of the mistakes people make.

The serving size appears as a household measure, such as 1 cup or 1 package, followed by the weight in grams. The gram figure is the one that lets you compare two different products, because household measures vary between brands and grams do not.

The serving size is not a recommendation. FDA states the rule plainly: by law, serving sizes are based on the amount of food people typically eat, not on how much they should eat. FDA's own teaching example is a frozen lasagna listed at 1 cup per serving, 4 servings per container, with 850 mg of sodium in a serving. Eat 2 cups and you have eaten 1,700 mg.

Whether a tray counts as one serving is decided by a rule rather than by the manufacturer's judgment. A product packaged and sold individually that contains less than 200 percent of the reference amount for its food category must be labeled as a single serving. Those reference amounts are set in the regulations. For frozen mixed dishes they are 1 cup for foods measurable in a cup, such as casseroles, macaroni and cheese, and pot pies, and 140 grams for mixed dishes that cannot be measured in a cup, such as burritos, enchiladas, pizza, and sandwiches, with another 55 grams added for products that carry gravy or a sauce topping.

That arithmetic explains a lot of what you see. Most single serve trays are labeled as one serving. Larger family trays and bags carry several. A full size frozen pizza is several servings, because the reference amount is 140 grams, which is roughly a slice or two, so the sodium figure describes a portion of the pizza and not the pizza.

Some packages that fall in between show two columns, one for a serving and one for the entire container. When a package gives you that second column, use it. When it does not, multiply before you decide.

What the sodium number means once you have it

The Daily Value FDA uses for sodium on every label is less than 2,300 mg a day. The percent Daily Value column, written as %DV, tells you what share of that amount one serving supplies. FDA's rule of thumb is that 5 percent DV or less of a nutrient per serving is low and 20 percent DV or more is high.

For sodium, 20 percent DV works out to 460 mg. Plenty of frozen dinners sit well above that, which is why the %DV on a single tray often reads 30, 40, or 50 percent. The figure is not a verdict on the food. It is a measurement, and it is only useful next to the rest of your day.

Two more facts about that number are worth carrying into the store:

1. 1 Sodium is rounded on the label. Above 140 mg it is printed to the nearest 10 mg increment, so a 10 mg difference between two products is a tie rather than a win. Below 140 mg it is rounded to the nearest 5 mg, and anything under 5 mg may be printed as zero.
2. 2 The sodium Daily Value does not move with calories. The footnote at the bottom of the label refers to a 2,000 calorie day, but 2,300 mg is the reference for sodium either way. A 260 calorie meal and a 640 calorie meal are measured against the same number.

The American Heart Association recommends no more than 2,300 mg of sodium a day and describes 1,500 mg as an optimal goal for most adults. If your own target is closer to 1,500, the printed %DV understates your share by about half again. A meal at 30 percent DV, which is 690 mg, is closer to 46 percent of a 1,500 mg day.

The amounts federal rules already treat as a lot in one meal

The labeling regulations draw lines that were written for manufacturers but work well as yardsticks for shoppers.

FDA defines a meal product as one weighing at least 10 ounces per labeled serving that contains at least three 40 gram portions of food drawn from two or more of four groups: grains, fruits and vegetables, dairy, and protein foods such as meat, fish, beans, eggs, or nuts. A main dish product weighs at least 6 ounces and contains at least 40 grams from each of two of those groups. Most frozen dinners land in one of these two categories.

Inside the rules that govern claims on food packages, FDA sets disclosure levels for those categories: more than 960 mg of sodium per labeled serving for a meal product and more than 720 mg for a main dish product. A label crossing those levels has to point shoppers toward the nutrition information for sodium. You can borrow the numbers directly. A frozen dinner above 960 mg is high by the government's own accounting, whatever the front of the box says.

A newer benchmark is considerably tighter. FDA's updated definition of the word healthy on a food package, published in December 2024, caps sodium at 690 mg for a meal product, 345 mg for a mixed product, and 230 mg for an individual food. Using the claim is voluntary and manufacturers have until February 25, 2028 to meet the new criteria, so packages following the old definition and the new one will sit side by side for a while. The number is still useful today: 690 mg is 30 percent of the sodium Daily Value, and it is the ceiling federal regulators chose for a meal carrying that word.

As packaged or as prepared

Some frozen products print two sets of numbers, one describing the food as packaged and one as prepared. The as prepared column assumes you follow the directions and add whatever they call for.

If the box contains a sauce packet or a seasoning packet and the directions tell you to use it, the as prepared column is the one that describes your dinner. If the directions call for butter, oil, milk, or a splash of soy sauce, those additions are built into that column too. Check which set of numbers you are reading before comparing two products, because holding one product's as packaged figure against another's as prepared figure is not a comparison.

Sodium does not cook off. Microwaving, baking, or air frying a tray does not lower the number on the label, and there is no way to rinse a composed meal the way you can rinse some canned foods. Whatever the panel says is what reaches the plate.

What the words on the front of the box are allowed to mean

Every sodium claim on a package has a fixed legal definition. Low sodium means 140 mg or less per reference amount, a level almost no composed frozen dinner reaches. Reduced sodium or less sodium means at least 25 percent less than a stated comparison food, which can still leave a large absolute number on a very salty product. Light in sodium means at least 50 percent less. No salt added describes what happened during processing, not the sodium content of the finished food.

Read the front panel as a pointer and the Nutrition Facts panel as the answer. A separate article in this series works through each of these claim definitions and the fine print that has to accompany them.

Reading the ingredient list for sodium you would not guess

The sodium figure on the Nutrition Facts panel already counts every source of sodium in the food, so the ingredient list will not change the total. It tells you something else: where the sodium is coming from, and whether a lower version of the same dish is even plausible.

Ingredients appear in order by weight. Salt near the top of a short list means a lot of it. Sodium also arrives through ingredients that do not read as salt, including monosodium glutamate, sodium phosphate, sodium nitrite, sodium benzoate, baking soda (which is sodium bicarbonate), soy sauce, broth, and the brine or solution added to some meat and poultry. None of that is unusual, and all of it is already in the total. Seeing it simply explains why the number is what it is.

This is also why taste is unreliable. FDA points out that some foods that do not taste salty can still be high in sodium. A separate article in this series covers that problem in full.

A routine for the freezer aisle

The whole check fits into six steps, and after a few trips it takes seconds.

1. 1 Read servings per container first, then decide whether you will eat one serving or the whole tray.
2. 2 Note the serving size in grams. This is what makes two boxes comparable.
3. 3 Read sodium in milligrams and multiply by the number of servings you will actually eat.
4. 4 Check the %DV, remembering that it is built on 2,300 mg and that your own target may be lower.
5. 5 If the two products have different serving weights, divide the sodium by the serving weight in grams and multiply by 100. That gives sodium per 100 grams, and the smaller number is the lower sodium food.
6. 6 Treat any difference of 10 mg or less as a tie.

The per 100 gram step takes a few seconds on a phone calculator and it is the only honest way to compare a 227 gram tray with a 283 gram tray. Photographing labels is a reasonable alternative if your hands are full or the print is small, and it also lets someone else in the household do the shopping with the same information. A separate article covers the comparison arithmetic in more depth, and another offers a simple way to record what you find so you are not repeating the work every trip.

Recipes change, so a check is worth repeating every so often. FDA's voluntary sodium reduction targets, finalized in 2021 for 163 categories of packaged and restaurant food, ask manufacturers to bring levels down over time. Using 2022 data, FDA reported that about 40 percent of those first targets had already been met or come close. A draft second phase issued in August 2024 would push average intake toward 2,750 mg a day and had not been finalized as of FDA's last update to that page. The practical effect is that a product you ruled out two years ago may carry a different label now, and one you rely on may have changed as well.

Budgeting the rest of the day around one meal

A frozen dinner at 1,000 mg is about 43 percent of the 2,300 mg Daily Value and roughly two thirds of the 1,500 mg the American Heart Association describes as an optimal goal. That does not put it out of reach. It turns the rest of the day into a set of smaller decisions: what goes alongside it, what the other two meals look like, and how often that particular tray comes up in a week.

The American Heart Association says that for most people, cutting back by 1,000 mg a day can improve blood pressure. The 2025 American Heart Association and American College of Cardiology high blood pressure guideline estimates that sodium reduction is associated with a fall of roughly 6 to 8 mm Hg in systolic pressure, the top number, among adults with high blood pressure. Those are averages drawn across many studies, and individual responses vary.

Two habits do more than finding one perfect box. The first is to learn the sodium content of the three or four frozen meals you buy most often and quietly rotate toward the lower ones. The second is to read the plain frozen items too. Some frozen vegetables, fish, and poultry are packed with added salt or a sodium solution and some are not, and the only way to know is the number on the panel.

One last point about that 2,300 mg figure: it is a labeling reference value, not a personal target. If you have kidney disease or heart failure, or you take a diuretic (a water pill) or another medicine that affects sodium or potassium balance, ask your health care professional or pharmacist what number applies to you. Yours may be lower, and knowing it changes how you read every label in the freezer case.