Magnesium glycinate has become one of the most talked-about sleep and stress supplements — but the number on the bottle is almost never the number that matters for dosing. Here's why, based on NIH Office of Dietary Supplements guidance, plus a free magnesium glycinate dosage calculator that does the conversion for you.
Elemental magnesium vs compound weight
Supplement labels typically list the total weight of the compound — "1,000 mg magnesium glycinate" — not the actual magnesium your body absorbs. Magnesium glycinate is only about 14% elemental magnesium by weight, so that 1,000 mg capsule contains roughly 140 mg of actual elemental magnesium. NIH's dosing guidance (both the RDA and the upper limit) is defined in elemental magnesium, so if you're dosing off the label number directly, you could be significantly under- or over-shooting the target without realizing it.
How much magnesium glycinate should I take
The NIH-listed RDA for total elemental magnesium (from food and supplements combined) is 310–420 mg/day depending on your age and sex — 400 mg/day for men 19–30, 420 mg/day for men 31+; 310 mg/day for women 19–30, 320 mg/day for women 31+. Converting a 300 mg elemental magnesium target into magnesium glycinate means looking for roughly 2,140 mg of the compound on the label (300 ÷ 0.14) — not 300 mg of glycinate.
Magnesium glycinate for sleep dosage
Consumer and clinical guides commonly cite 200–400 mg of elemental magnesium taken 30–60 minutes before bed as the most-used protocol for sleep support. Our calculator caps that range at 350 mg to stay within the NIH-listed upper limit for supplemental magnesium.
Why we don't push a specific product
A lot of the dosage guides you'll find online are published by companies that sell their own magnesium glycinate supplement — which creates an obvious incentive to frame "the right dose" around their product's serving size. This calculator doesn't sell magnesium, link to a specific brand, or require an account — it's purely the NIH numbers, converted for you.
The upper limit that matters
NIH's Office of Dietary Supplements lists 350 mg/day of elemental magnesium from supplements alone (not counting food) as the tolerable upper intake level for adults — going meaningfully above it raises the risk of diarrhea and GI upset without added benefit. If you're also getting magnesium from a multivitamin or other supplement, add those elemental amounts together before comparing against this limit.
Try the Magnesium Glycinate Dosage Calculator → · Also supplementing creatine? See the Creatine Dosage Calculator.
Sources: NIH Office of Dietary Supplements, "Magnesium — Health Professional Fact Sheet" (accessed 2026-09-22). This is general nutrition information, not medical advice — talk to a doctor before starting a new supplement, especially if you take other medications or have kidney issues.
