Elemental Magnesium Calculator
A label that says "magnesium glycinate 500 mg" is often giving the weight of the whole compound. Only part of that is magnesium. Pick the form, enter the weight, and this works out the elemental magnesium from the compound's chemical formula.
Glycinate (bisglycinate) is 14.1% magnesium by weight (Mg(C2H4NO2)2).
70 mg elemental magnesium per serving
70 mg a day
That is within the 350 mg a day upper limit for magnesium from supplements. The sleep trial of magnesium bisglycinate used 250 mg a day.
Products labelled 'buffered' also contain magnesium oxide, which raises the figure.
Elemental magnesium by form
Each percentage is the share of the compound's weight that is magnesium, calculated from its formula and standard atomic weights.
| Form | Formula | Magnesium by weight | In 500 mg of compound |
|---|---|---|---|
| Oxide | MgO | 60.3% | 302 mg |
| Hydroxide | Mg(OH)2 | 41.7% | 208 mg |
| Carbonate | MgCO3 | 28.8% | 144 mg |
| Citrate | Mg3(C6H5O7)2 | 16.2% | 81 mg |
| Malate | MgC4H4O5 | 15.5% | 78 mg |
| Glycinate (bisglycinate) | Mg(C2H4NO2)2 | 14.1% | 70 mg |
| Chloride (hexahydrate) | MgCl2·6H2O | 12.0% | 60 mg |
| Lactate (dihydrate) | Mg(C3H5O3)2·2H2O | 10.2% | 51 mg |
| Sulfate (Epsom salt, heptahydrate) | MgSO4·7H2O | 9.9% | 49 mg |
| Taurate | Mg(C2H6NO3S)2 | 8.9% | 45 mg |
| Aspartate | Mg(C4H6NO4)2 | 8.4% | 42 mg |
| L-threonate | Mg(C4H7O5)2 | 8.3% | 41 mg |
| Gluconate | Mg(C6H11O7)2 | 5.9% | 29 mg |
What to compare the result with
- The upper limit for magnesium from supplements and medicines is 350 mg a day for adults, according to the US National Institutes of Health Office of Dietary Supplements. Magnesium from food does not count towards it.
- The one placebo-controlled sleep trial of magnesium bisglycinate used 250 mg of elemental magnesium a day (PMID 40918053). See our guide to magnesium for sleep.
- A higher elemental figure is not the same as better absorption. Oxide has the most magnesium by weight and is among the less well absorbed forms.
Limits of the calculation
The figures assume the pure compound named. Real powders can be hydrated, which lowers the magnesium content, or buffered with magnesium oxide, which raises it. Where the Supplement Facts panel states an elemental amount, that number is the one to use.
Frequently Asked Questions
What is elemental magnesium?
It is the weight of the magnesium itself, without the glycine, citric acid, oxygen or whatever else it is bound to. Dose advice and safety limits are always given as elemental magnesium.
How much elemental magnesium is in 500 mg of magnesium glycinate?
About 70 mg. Pure magnesium bisglycinate is 14.1% magnesium by weight. Products labelled 'buffered' add magnesium oxide and contain more.
Which form of magnesium has the most elemental magnesium?
Magnesium oxide, at about 60% by weight. It is also one of the less well absorbed forms, so a high elemental figure does not mean more reaches your blood.
Should I trust the calculator or the label?
The label. If the Supplement Facts panel gives an elemental figure, such as 'Magnesium (as magnesium bisglycinate) 100 mg', use that number. This calculator is for labels that only give the weight of the compound.
Medical disclaimer: This content is for informational purposes only and is not medical advice. Supplements are not intended to diagnose, treat, cure, or prevent any disease. Individual results vary. Consult a qualified healthcare professional before starting any supplement, especially if you are pregnant, nursing, taking medication, or have a medical condition.