Magnesium — FDA Daily Value
The FDA Daily Value for Magnesium is 420 mg for adults and children 4 or more years of age — a Reference Daily Intake (RDI), a fixed target not tied to calories. It changes by population group; see the exact numbers below.
A serving with 126 mg of magnesium provides 126 ÷ 420 × 100 = 30% DV (High).
Magnesium rounding rules
Amount
Magnesium is declared to the nearest 5mg — measuring finer than that changes nothing on the label.
| Amount range | Rounding rule |
|---|---|
| ≥0 | nearest 5mg |
% Daily Value
| %DV range | Rounding rule |
|---|---|
| 0 to 10 | nearest 2% |
| >10 to 50 | nearest 5% |
| >50 | nearest 10% |
How much Magnesium is behind each %DV?
What a serving has to contain for a label to print each figure. The %DV is worked out from the actual amount, before that amount is rounded.
| If the label shows | The serving must contain |
|---|---|
| Nearest 2%0 to 10% DV | |
| 0% DV | 0 mg≤ amount <4.2 mg |
| 2% DV | 4.2 mg≤ amount <12.6 mg |
| 4% DV | 12.6 mg≤ amount <21 mg |
| 6% DV | 21 mg≤ amount <29.4 mg |
| 8% DV | 29.4 mg≤ amount <37.8 mg |
| 10% DV | 37.8 mg≤ amount <52.5 mg |
| Nearest 5%>10 to 50% DV | |
| 15% DV | 52.5 mg≤ amount <73.5 mg |
| 20% DV | 73.5 mg≤ amount <94.5 mg |
| 25% DV | 94.5 mg≤ amount <115.5 mg |
| 30% DV | 115.5 mg≤ amount <136.5 mg |
| 35% DV | 136.5 mg≤ amount <157.5 mg |
| 40% DV | 157.5 mg≤ amount <178.5 mg |
| 45% DV | 178.5 mg≤ amount <199.5 mg |
| 50% DV | 199.5 mg≤ amount <231 mg |
| Nearest 10%>50% DV | |
| 60% DV | 231 mg≤ amount <273 mg |
| 70% DV | 273 mg≤ amount <315 mg |
| 80% DV | 315 mg≤ amount <357 mg |
| 90% DV | 357 mg≤ amount <399 mg |
| 100% DV | 399 mg≤ amount <441 mg |
The rules are FDA's; the inversion is ours. Ranges are inclusive at the low end and exclusive at the high end, because an exact half rounds up.
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Frequently asked questions
Every figure on this page traces to a paragraph of 21 CFR 101.9. These are those paragraphs, in full.
What is the FDA Daily Value for Magnesium?
The FDA Daily Value for Magnesium is 420 mg for adults and children 4 years and older, per 21 CFR 101.9. On a Nutrition Facts label, a serving's %DV for magnesium is its amount divided by 420 mg, times 100.
How are vitamin and mineral %DV values rounded?
The percentages for vitamins and minerals shall be expressed to the nearest 2-percent increment up to and including the 10-percent level, the nearest 5-percent increment above 10 percent and up to and including the 50-percent level, and the nearest 10-percent increment above the 50-percent level.
Note: Amount increments for vitamins and minerals come from FDA Guidance 2018/2019, not from CFR text.
Where do the Daily Values for vitamins and minerals come from?
The following RDIs, nomenclature, and units of measure are established for the following vitamins and minerals which are essential in human nutrition:
Note: The Daily Value itself is listed in the RDI table this paragraph introduces, not restated as prose.
How do I find out how much magnesium is in a food?
A Daily Value is a reference target, not a measurement of any particular food. To find the magnesium content of a specific ingredient or product, look it up in USDA FoodData Central, then use that amount here to see what a label would declare and what %DV it carries.
Other nutrients
Every nutrient a Nutrition Facts label can carry, with the FDA rounding rules that govern it.
Vitamins & minerals
Macronutrients
Voluntary — no Daily Value
For informational purposes only; verify against § 101.9(c)(8)(iv). · US Nutrition Label Rules v1.3.0 · CFR snapshot 2026-02-12