Magnesium bisglycinate label says 1,000 mg but I only want 140 mg elemental. How do I do the math?

This is one of the most common label-reading questions. Pure magnesium bisglycinate (anhydrous, molecular weight about 172.4) is roughly 14.1% elemental magnesium by weight, because magnesium is about 24.3 of that 172.4. So 1,000 mg of the compound gives about 141 mg elemental, and 2,000 mg gives about 282 mg. Always check the Supplement Facts panel. It should list elemental magnesium per serving, for example 'Magnesium (as bisglycinate) 140 mg'. Some products are buffered with magnesium oxide, so the label may show a higher elemental number than the chelate alone would give. Compare that number with 350 mg/day, the NIH upper limit for supplemental magnesium in adults. That limit counts supplements and medications, not food. Split doses if you take more than about 200 mg at once.