Every number on a nutrition label is per serving. Which makes the serving size the master dial — turn it down, and every scary number shrinks with it.
The classics: a small bag of chips that's 'two servings' (who shares?). A pint of ice cream at '3 servings' so the label reads 280 calories instead of 840. Cooking spray listing '0 calories' because a serving is a quarter-second spritz — the FDA lets anything under 5 calories per serving round to zero, so a fully caloric oil can legally wear a zero [1].
Regulators have pushed back: US serving sizes must now reflect what people 'customarily consume,' and packages between one and two servings (like a 15oz soda) must be labeled as one [1]. Better — but 'customarily consume' is still a negotiation, and multi-serving packaging still does the heavy lifting.
The same trick works in reverse on good nutrients: a cereal can advertise its protein using a serving size nobody pours, twice.
How rootd sidesteps the whole game: our low/moderate/high judgments are computed per 100 grams — the same yardstick for every product — so a tiny official serving can't hide a sugary recipe [2]. The per-serving numbers are shown too, because that's what you'll actually eat, but the verdict comes from the standardized view.
Ten-second habit: when a label impresses you, check the serving size first. Ask whether the number of servings in the package matches the number of humans who will realistically eat it.