Reading US Nutrition Labels in Metric (Grams & Milliliters)
US Nutrition Facts labels report nutrients in metric units - grams and milligrams - plus milliliters for some liquids. Learn what each number means and how to convert it.
Why US Food Labels Are Already Metric
Even though Americans measure recipes in cups and pounds, the Nutrition Facts label is built on the metric system. Every nutrient amount - total fat, saturated fat, cholesterol, sodium, total carbohydrate, sugars, and protein - is listed in grams (g) or milligrams (mg). A milligram is one thousandth of a gram, so 500 mg of sodium is the same as 0.5 g. The grams to milligrams converter makes that shift instantly.
Using metric here is not a quirk. Grams and milligrams are exact, scalable units that let you compare a tiny 5 mg cholesterol figure against a 30 g protein figure on the same logic. The metric label also pairs with household measures: a serving might read "1 cup (240 g)" so you see both the spoon measure and the weight.
The Nutrients Listed in Grams and Milligrams
Most macros and minerals on the label use grams: total fat, saturated fat, trans fat, total carbohydrate, dietary fiber, total sugars, added sugars, and protein are all in grams. A few are small enough to use milligrams: cholesterol and sodium are reported in mg because a gram would be an awkward large number for everyday portions.
When a recipe or a doctor tells you to stay under, say, 2,300 mg of sodium per day, that is 2.3 g. Converting between the two with the gram to milligram converter keeps your daily tracking honest instead of mixing units by hand.
Where Milliliters Appear
Liquids on some labels - such as the volume of a drink or a liquid supplement - may be shown in milliliters (mL) or liters (L). A 250 mL serving is a quarter of a liter; the milliliters to liters converter handles that. Most solid foods stay in grams, but any fluid measure on the panel follows the same metric pattern.
Percent Daily Value (%DV)
Next to each nutrient is a %DV, which shows how much one serving contributes to a daily diet of 2,000 calories - the reference the FDA uses for the standard label. It is a percentage, not a weight, so it does not need conversion; it is a quick way to see whether a serving is high (20% or more) or low (5% or less) in a nutrient.
Putting the Label to Work
To track intake across brands, convert everything to one unit first. Keep fats, carbs, and protein in grams, and cholesterol and sodium in milligrams, then sum across the day. If a second product lists sodium in grams, convert it to milligrams before adding so the totals line up. The ounce to milliliter converter helps when a package also prints an imperial measure you want to sanity-check against the metric panel.
Frequently Asked Questions
Are US nutrition labels in metric or imperial?
They are metric. Nutrients are listed in grams and milligrams, and some liquid volumes in milliliters or liters, even though kitchen measuring uses cups and ounces.
How many milligrams are in a gram on a food label?
1,000. So 500 mg of sodium equals 0.5 g. The label uses milligrams for small amounts like sodium and cholesterol and grams for larger amounts like fat and protein.
What does %DV mean on a nutrition label?
Percent Daily Value shows how much a serving contributes to a 2,000-calorie daily diet. It is a percentage, not a weight, and needs no unit conversion.
Quick Summary
US Nutrition Facts labels are metric at their core: grams for macros and milligrams for sodium and cholesterol, with milliliters for liquids. Converting between g and mg is the key to accurate daily tracking.
Related Guide
oz to ml: Convert Fluid Ounces to Milliliters
Convert oz to ml: one US fluid ounce equals 29.57 ml. Learn the exact factor, how it is used in recipes and bottle sizes, and common fluid-ounce-to-ml values.
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Disclaimer
Unit conversions on this site use internationally recognized, fixed conversion factors (for example, 1 inch = 2.54 cm, 1 pound = 0.45359237 kg, 1 °F = (°C × 9/5) + 32). They are provided for general, informational, and educational use. For applications where accuracy is critical — such as medical dosing, engineering, scientific research, trade, or legal compliance — always verify results against authoritative sources such as the U.S. National Institute of Standards and Technology (NIST) and the official International System of Units (SI) brochure, and follow any applicable local standards.
Exact Constants & Authoritative Sources
Every conversion on this page uses the fixed, internationally agreed constants below — drawn from NIST and the SI Brochure. No values are estimated or rounded as if exact. See the full list on our Sources & Standards page.
- EXACT1 pound (lb, avoirdupois) = 0.45359237 kilograms (exact)
- EXACT1 ounce (oz, avoirdupois) = 28.349523125 grams (exact, 1/16 lb)
- EXACT1 stone (st) = 6.35029318 kilograms (exact, 14 lb)
- EXACT1 short ton (US) = 907.18474 kilograms (exact, 2000 lb)
Common Pitfalls & How to Avoid Them
Mass vs. weight
The pound and kilogram are units of MASS, not force. On Earth, mass and "weight" read the same number in practice, but a 70 kg mass weighs less on the Moon. UnitFig converts mass; for scientific force you need newtons (1 lbf = 4.4482216152605 N, exact).
Avoirdupois vs. troy ounce
Cooking and body weight use the avoirdupois ounce (28.349523125 g). Gold and precious metals use the troy ounce (31.1034768 g). Never mix them — the error is about 10%.
Rounding the factor
Using 2.2 instead of the exact 2.20462262 overstates small errors at large values. For medical dosing or competition weight classes, keep the full factor or use a converter.
A unit-conversion reference site has no manufacturer-specific or device calibration parameters, so "layered tuning" does not apply here. The only real error-handling is input validation: the converter rejects non-numeric, empty, or out-of-range entries and shows a clear message, then falls back to exact constants above. No estimated or rounded figures are ever presented as exact.
Authoritative sources for this page
- NIST (U.S. National Institute of Standards and Technology) — NIST SP 330 — The International System of Units (SI), 2019 edition
Last Updated 2026 | This article was reviewed for accuracy