14.1% at most. Pure magnesium bisglycinate is 14.1% elemental magnesium by weight: magnesium weighs 24.31 g/mol and the whole molecule weighs 172.42 g/mol. So 1,000 mg of magnesium glycinate supplies no more than 141 mg of magnesium.
Grades that hold water are lower, 12.8% as the monohydrate and 11.7% as the dihydrate. A label ratio of 18%, 20% or 22% is inconsistent with pure anhydrous bisglycinate if both label figures are accurate and on the same weight basis. It is a reason to check the ingredient list and ask the manufacturer.
The calculation
Magnesium glycinate is one magnesium ion bonded to two glycine molecules, written Mg(C2H4NO2)2. Anyone can check the arithmetic with a periodic table:
| Form of magnesium bisglycinate | Molar mass | Magnesium by weight |
|---|---|---|
| Anhydrous (no water) | 172.42 g/mol | 24.31 ÷ 172.42 = 14.1% |
| Monohydrate | 190.43 g/mol | 12.8% |
| Dihydrate | 208.45 g/mol | 11.7% |
The 14.1% figure is a ceiling set by the molecule, not a quality grade. No manufacturing process can raise it, because glycine is heavy and every magnesium ion comes with two of them. Water only adds weight, so pure material should not measure materially above the ceiling, allowing for measurement uncertainty.
Measured, not only calculated
In September 2026 an independent NABL-accredited laboratory assayed a lot of chelated magnesium bisglycinate raw material at 14.01% magnesium by weight, with 0.73 g/100 g moisture on the same lot. That is 99.4% of the theoretical maximum and compatible with bisglycinate composition, but a total-magnesium assay does not prove chemical identity, rule out other magnesium sources or show the percentage chelated. The report is published as open data, with batch and ULR numbers, in our magnesium lab testing dataset.
Every common form, by percentage
Denser forms carry more magnesium per milligram. The last column shows how much of each compound it takes to supply 100 mg of elemental magnesium.
| Form | Magnesium by weight | Compound for 100 mg Mg |
|---|---|---|
| Magnesium oxide | 60.3% | 166 mg |
| Magnesium hydroxide | 41.7% | 240 mg |
| Magnesium carbonate | 28.8% | 347 mg |
| Magnesium citrate | 16.2% | 619 mg |
| Magnesium malate | 15.5% | 643 mg |
| Magnesium bisglycinate | 14.1% | 709 mg |
| Magnesium lactate | 12.0% | 833 mg |
| Magnesium taurate | 8.9% | 1,122 mg |
| Magnesium L-threonate | 8.3% | 1,212 mg |
Anhydrous forms, calculated from molar masses and rounded. Commercial lots vary with moisture content.
Why some glycinate labels say 18%, 20% or 22%
Pure anhydrous bisglycinate cannot pass 14.1%, so on a comparable weight basis a higher ratio is inconsistent with it if both label figures are accurate. Buffered or blended grades reach these figures by adding a denser magnesium source, such as magnesium hydroxide, and should declare it. A buffered grade is permitted in India, but the label should say so: every magnesium source named in the ingredient list, and elemental magnesium stated per serving. Arithmetic alone cannot identify an undeclared ingredient. We explain the difference in detail in 22% vs 14% magnesium glycinate, and whether it matters in Is buffered magnesium glycinate bad?
Check any label in ten seconds. Our magnesium label calculator takes the compound weight and the elemental magnesium from any jar, works out the percentage, and tells you whether that number is possible for a single ingredient or only for a blend.
Related reading: How much elemental magnesium is in 500 mg of magnesium glycinate? · What does "fully chelated" mean on a magnesium label?
This article is educational and is not medical advice. Magnesium supplements are not intended to diagnose, treat, cure or prevent any disease. Consult a qualified healthcare professional before starting any supplement, particularly if you are pregnant, breastfeeding, have kidney disease, or take prescription medications. Percentages are calculated from standard atomic weights; commercial lots vary with moisture content.