Every calorie number in our calculators comes from the restaurant’s own published nutrition information. But how does a chain arrive at “580 calories” for a Big Mac in the first place, and how exact is it? Here is what the numbers are, and what they are not.
The rule chains follow in the U.S.
Since 2018, U.S. restaurant chains with 20 or more locations have had to post calories on their menus and menu boards and to provide more nutrition information (fat, carbohydrate, protein, sodium and more) in writing on request. That is the FDA’s menu labeling rule. The rule does not make chains send every item to a lab. It asks for a “reasonable basis” for the numbers, and lists the accepted methods: nutrient databases, cookbooks, laboratory analyses and other reasonable means, such as the Nutrition Facts label on a packaged ingredient.
In practice most chains calculate: they take the standard recipe (how many grams of patty, bun, cheese and sauce), look up each ingredient in a nutrient database or the supplier’s data, and add it up. Some test finished items in a lab as well. Either way the number describes the standard recipe, not the exact sandwich you get on a given day.
Why the numbers are round
Menu calories are rounded: to the nearest 5 calories up to 50, and to the nearest 10 above that. That is why almost every item ends in a zero. Five Guys is an exception in our data because it publishes nutrition by component (bun, patty, toppings) and we add those parts up, so its totals end in other digits, such as 844 calories for a Hamburger.
When calories and macros don’t add up
A gram of protein or carbohydrate gives about 4 calories and a gram of fat about 9 (the Atwater factors). If you multiply out an item’s protein, carbs and fat you usually land close to the published calories, but rarely exactly: fiber gives fewer calories than other carbs, each value is rounded on its own, and a calculated recipe can use different factors. We checked every item in our calculators this way. These are the ones where the gap is largest:
| Item | Restaurant | Published calories | From protein, carbs and fat | Difference |
|---|---|---|---|---|
| Hamburger (bun + 2 patties) | Five Guys | 844 | 674 | +20% |
| Sweet Kernel Corn (family) | KFC | 280 | 331 | -18% |
| Little Hamburger (bun + 1 patty) | Five Guys | 542 | 457 | +16% |
| Corn on the Cob (family) | KFC | 280 | 322 | -15% |
| Loaded Baked Potato Soup with Bacon (8 oz bowl) (participating locations) | Subway | 200 | 230 | -15% |
| Red Beans & Rice (Large) | Popeyes | 640 | 724 | -13% |
| Chicken Breast (Classic or Spicy) | Popeyes | 620 | 546 | +12% |
| Red Beans & Rice (Regular) | Popeyes | 260 | 288 | -11% |
A gap of a few percent is normal. The Five Guys burgers stand out because the guide’s own calorie and macro figures do not match each other. We show the restaurant’s official numbers as published and note this on the Five Guys calculator, rather than “correcting” them ourselves.
How much can the real food differ?
Portions are made by hand, so the fries in your bag or the sauce on your sandwich will not weigh exactly what the recipe says. Restaurants also change recipes and suppliers. That is why we show the date we last checked each chain, link to the official source on every calculator page, and log every change on Menu Changes. Treat any single number as a good estimate of a standard serving, not a lab result for your meal.
What this means when you order
- Compare like with like: published numbers are most useful for comparing items on the same menu, which were all worked out the same way.
- Customizations change everything. “No mayo” or “extra cheese” is not in the base number; our calculators add the add-ons the chain publishes.
- Check the date. Our methodology page lists when every dataset was last checked against the official source.
Sources
- FDA: Menu Labeling Requirements
- 21 CFR 101.11: Nutrition labeling of standard menu items in covered establishments
- Menu figures: each restaurant’s official U.S. nutrition information, as linked on the methodology page.