What 100 mg of magnesium weighs

Food mass per 100 mg elemental magnesium

These 25 USDA FoodData Central records, retrieved 2026-09-13, give magnesium per 100 g of the described edible food; dividing 10,000 by that value gives the food mass containing 100 mg magnesium.

The exact USDA descriptions control the comparison: almond flour is shown as almond flour, cooked foods include their water, and raw seed kernels are measured as recorded. Each value belongs to that preparation and source record. Food mass is rounded to 0.1 g in the table and to whole grams in the opening sentence.

Compound mass for the same 100 mg of magnesium

The 15 salt formulas in the site's chemistry table require 166–1706 mg of compound per 100 mg elemental magnesium, calculated 2026-09-13; hydration-ambiguous salts retain their full interval.

Compound mass = 100 mg ÷ elemental fraction. For an interval, divide by the largest fraction for the smallest mass and by the smallest fraction for the largest mass. These are compound masses before capsule shells, excipients or other ingredients; they are not whole-tablet weights.

The capsule-label working

These 15 NIH DSLD label examples reach at least 100 mg declared elemental magnesium in 1, 2 or 3 whole capsules, calculated 2026-09-13 from the label's magnesium and fixed capsule count per serving; five examples per count are selected by ascending DSLD identifier.

Elemental mg per capsule = filed elemental mg per serving ÷ capsules per serving. Whole-capsule count rounds 100 ÷ mg per capsule upward, so the resulting amount may exceed 100 mg. These examples are an explicitly selected subset, not the full range of filed capsule amounts. The calculation transcribes label declarations and does not measure the contents of a capsule.

Three corrected USDA search matches

On 2026-09-13, 3 search matches were corrected to named Standard Reference foods: boiled spinach, oats cooked with water, and Atlantic farmed salmon cooked with dry heat.

• Spinach, cooked, boiled, drained, without salt: FDC 168463, 87 mg magnesium per 100 g. USDA ARS nutrient report, NDB 11458.
• Cereals, oats, regular and quick, unenriched, cooked with water (includes boiling and microwaving), without salt: FDC 173905, 27 mg magnesium per 100 g. USDA ARS nutrient report, NDB 08121.
• Fish, salmon, Atlantic, farmed, cooked, dry heat: FDC 175168, 30 mg magnesium per 100 g. USDA ARS nutrient report, NDB 15237.

These tables equate elemental mass only. They do not equate absorption or compare outcomes. Published measurement methods and populations are documented on the absorption studies page; formula and capsule-capacity working is on the label mass-budget audit.

Trace the evidence

3 reference sections document how these records are interpreted as of 2026-09-13: methodology and evidence tiers for source and calculation boundaries, the label mass-budget audit for compound and capsule arithmetic, and absorption studies for measurements under each study's conditions.