Magnesium Dose By Form Calculator
Convert an elemental magnesium target into the actual compound milligrams you need — because oxide, citrate and glycinate carry very different amounts of usable magnesium.
How it works
Compound mg = elemental target ÷ elemental fraction · (e.g. oxide 60.3%, citrate 16.2%, glycinate 14.1%)
Supplement labels sometimes list the whole-compound weight and sometimes the elemental magnesium, and the two can differ several-fold. Magnesium oxide is about 60% elemental magnesium by weight while glycinate is only about 14%, so 500 mg of one is nothing like 500 mg of the other. Divide your elemental target by the form’s elemental fraction to find how many milligrams of that specific compound to take — bioavailability and gut tolerance also differ by form.
Worked example
For a 200 mg elemental target using magnesium glycinate (14.1% elemental), you need 200 ÷ 0.141 = about 1,418 mg of the glycinate compound. The same 200 mg from magnesium oxide would take only 200 ÷ 0.603 = about 332 mg — though oxide is absorbed less well.
Frequently asked questions
Which magnesium form is best?
It depends on the goal: glycinate is gentle and well absorbed, citrate can loosen stools (useful for constipation), and oxide is cheap but poorly absorbed. This tool handles the dosing; tolerance and purpose guide the choice.
Does the label already show elemental magnesium?
Reputable labels usually state elemental magnesium, but some list the compound weight. If the number seems high for the form, it is likely the compound weight — this calculator lets you reconcile the two.
What is a typical magnesium target?
Adult daily needs are often quoted around 310–420 mg total from food and supplements. Supplemental doses are commonly smaller, and very high doses can cause diarrhoea.
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Educational estimate, not medical advice. Talk to a doctor, pharmacist or registered dietitian before starting or changing any supplement, especially if you are pregnant, nursing, on medication or managing a health condition.