A magnesium compound's share of magnesium is 24.305 divided by its molar mass. That gives about 60% for magnesium oxide, 16% for trimagnesium dicitrate, 14.1% for bisglycinate (glycinate), 8.9% for taurate and 7 to 8% for L-threonate. So 400 mg of magnesium glycinate holds about 56 mg of elemental magnesium (400 × 0.14096 = 56.4). The table below shows the working for twelve forms.
Images are AI-generated and illustrative.
We sell one magnesium product, Satiovex Tri-Mag Night, which uses three of these forms. Satiovex Tri-Mag Night is a three-form magnesium capsule: magnesium bisglycinate, magnesium L-threonate and magnesium taurate, 200 mg of elemental magnesium per serving of three capsules, 90 capsules, 30 servings.
How do you calculate the elemental magnesium in a compound?
The NIH Office of Dietary Supplements says a US Supplement Facts panel declares elemental magnesium, not the weight of the whole compound, so each compound's magnesium share links the two numbers. Add the atomic weights of every atom in the formula to get the molar mass, then divide the weight of the magnesium atoms (24.305 each) by it. Compound weight times share gives elemental milligrams; elemental milligrams divided by the share give the compound weight.
For magnesium bisglycinate, C4H8MgN2O4, the molar mass is 4 × 12.011 + 8 × 1.008 + 24.305 + 2 × 14.007 + 4 × 15.999 = 172.423 g/mol. The share is 24.305 ÷ 172.423 = 0.14096, so 400 mg of compound holds 400 × 0.14096 = 56.4 mg of magnesium. For magnesium oxide, MgO, the molar mass is 24.305 + 15.999 = 40.304 and the share is 24.305 ÷ 40.304 = 0.60304.
The atomic weights are the abridged IUPAC values listed by CIAAW: H 1.0080, C 12.011, N 14.007, O 15.999, S 32.06, Cl 35.45, Mg 24.305. PubChem files "magnesium glycinate" and "magnesium bisglycinate" under one record, so the table treats them as one compound.
Elemental magnesium percentage by form: twelve forms compared
| Form | Formula | Molar mass, g/mol | Working: Mg ÷ molar mass | Compound for 100 mg of magnesium |
|---|---|---|---|---|
| Magnesium oxide | MgO | 40.304 | 24.305 ÷ 40.304 = 60.3% | 166 mg |
| Magnesium hydroxide | Mg(OH)2 | 58.319 | 24.305 ÷ 58.319 = 41.7% | 240 mg |
| Magnesium carbonate | MgCO3 | 84.313 | 24.305 ÷ 84.313 = 28.8% | 347 mg |
| Trimagnesium dicitrate | Mg3(C6H5O7)2 | 451.113 | 72.915 ÷ 451.113 = 16.2% | 619 mg |
| Magnesium malate | C4H4MgO5 | 156.376 | 24.305 ÷ 156.376 = 15.5% | 643 mg |
| Magnesium bisglycinate (glycinate) | C4H8MgN2O4 | 172.423 | 24.305 ÷ 172.423 = 14.1% | 709 mg |
| Magnesium lactate | Mg(C3H5O3)2 | 202.445 | 24.305 ÷ 202.445 = 12.0% | 833 mg |
| Magnesium chloride hexahydrate | MgCl2·6H2O | 203.295 | 24.305 ÷ 203.295 = 12.0% | 836 mg |
| Magnesium hydrogen citrate (1:1) | C6H6MgO7 | 214.412 | 24.305 ÷ 214.412 = 11.3% | 882 mg |
| Magnesium sulfate heptahydrate | MgSO4·7H2O | 246.466 | 24.305 ÷ 246.466 = 9.9% | 1,014 mg |
| Magnesium taurate | C4H12MgN2O6S2 | 272.573 | 24.305 ÷ 272.573 = 8.9% | 1,121 mg |
| Magnesium L-threonate, anhydrous | C8H14MgO10 | 294.495 | 24.305 ÷ 294.495 = 8.3% | 1,212 mg |
Each row follows the same sum from its formula, and rows without a water count are anhydrous. Shares are rounded to one decimal place, but the last column uses the unrounded share, so a hand check can differ by a milligram. Our comparison of bisglycinate, L-threonate and taurate covers what published studies examined.
Why do hydration and the word "citrate" change the answer?
Water of crystallisation adds weight but no magnesium, so a hydrate holds a smaller share than the same salt without water.
| Name on a label | Without extra water or a different salt | With water or as a different salt |
|---|---|---|
| Magnesium chloride | MgCl2, anhydrous: 25.5% | MgCl2·6H2O, hexahydrate: 12.0% |
| Magnesium sulfate | MgSO4, anhydrous: 20.2% | MgSO4·7H2O, heptahydrate: 9.9% |
| Magnesium L-threonate | C8H14MgO10, anhydrous: 8.3% | C8H16MgO11, monohydrate: 7.8% |
| Magnesium citrate | Trimagnesium dicitrate: 16.2% | Magnesium hydrogen citrate, 1:1: 11.3%; dicitrate nonahydrate: 11.9% |
"Citrate" is the sharper problem. PubChem files the name "magnesium citrate" under trimagnesium dicitrate (16.2%) and holds the 1:1 salt as a separate record, magnesium citrate dibasic (11.3%). The EU list of mineral sources for food supplements (Regulation (EC) No 1170/2009, Annex II) names "magnesium salts of citric acid" as a group. A label that says only "citrate" therefore does not fix the share: use its elemental line, or ask the maker which citrate it is.
L-threonate needs the same care. EFSA's 2024 opinion describes the ingredient it assessed as almost 100% magnesium L-threonate monohydrate, with magnesium at 7.5% to 8.8% across batches and a proposed specification of 7.2% to 8.3%. That range is why this page gives 7 to 8%.
Three examples with the working: compound to elemental and back
Take 200 mg of elemental magnesium as the target, the amount per serving on the Tri-Mag Night product page. Divide by the share to get the compound weight, then multiply back as a check. That product blends three forms, so no single row gives its compound weight.
| Compound | Share | Compound for 200 mg of magnesium | Check: back to magnesium |
|---|---|---|---|
| Magnesium bisglycinate | 0.14096 | 200 ÷ 0.14096 = 1,419 mg | 1,419 × 0.14096 = 200.0 mg |
| Magnesium oxide | 0.60304 | 200 ÷ 0.60304 = 332 mg | 332 × 0.60304 = 200.2 mg |
| Magnesium L-threonate (anhydrous) | 0.08253 | 200 ÷ 0.08253 = 2,423 mg | 2,423 × 0.08253 = 200.0 mg |
The same compound weight carries very different amounts of magnesium: 1,000 mg of oxide holds about 603 mg, bisglycinate about 141 mg and anhydrous L-threonate about 83 mg. Our label guide uses these shares to check a printed figure.
Price per 100 mg of elemental magnesium: our three packs
The price per 100 mg of elemental magnesium is the pack price divided by the pack's total elemental milligrams, times 100. That total is servings times elemental milligrams per serving. For Satiovex Tri-Mag Night, a bottle holds 30 servings of 200 mg, so 30 × 200 = 6,000 mg. Prices are our GBP base prices; checkout shows your local currency.
| Pack | Price, GBP | Servings | Working: price ÷ total elemental mg × 100 | Price per 100 mg |
|---|---|---|---|---|
| 1 bottle | 34.95 | 30 | 34.95 ÷ 6,000 × 100 = 0.5825 | £0.58 |
| 3 bottles | 84.95 | 90 | 84.95 ÷ 18,000 × 100 = 0.4719 | £0.47 |
| 6 bottles | 149.95 | 180 | 149.95 ÷ 36,000 × 100 = 0.4165 | £0.42 |
Larger packs lower the price per serving for the same 200 mg, so the figure falls. It is arithmetic only.
How do you calculate the cost per mg of elemental magnesium for any label?
- Find the elemental milligrams per serving, converting from a compound weight with the share in the table if needed.
- Multiply by the servings per container to get the elemental milligrams in the pack.
- Divide the pack price by that total and multiply by 100.
- Use the same currency and price basis for both products, such as price before delivery.
The result puts two labels on one measure but does not rank them, because form, capsule count and serving size still differ.
Questions about elemental magnesium by form
How much elemental magnesium is in 400 mg of magnesium glycinate?
About 56 mg. Magnesium glycinate (bisglycinate) is 14.1% magnesium by weight, so 400 × 0.14096 = 56.4 mg, assuming the 400 mg is the compound alone. A glycinate-only line that shows more than that implies another magnesium source, which the ceiling test in our label guide checks.
How much elemental magnesium is in magnesium oxide?
About 60%. 24.305 ÷ 40.304 = 0.603, so 400 mg of magnesium oxide holds about 241 mg of magnesium (400 × 0.60304 = 241.2).
How much elemental magnesium is in magnesium citrate?
It depends on which citrate. Trimagnesium dicitrate is 16.2%, so 1,000 mg holds about 162 mg. The 1:1 salt, magnesium hydrogen citrate, is 11.3%, about 113 mg. If the label does not name the compound, use its elemental line.
How much elemental magnesium is in magnesium taurate?
8.9%. 24.305 ÷ 272.573 = 0.08917, so 1,000 mg of magnesium taurate holds about 89 mg of magnesium.
What percentage of magnesium L-threonate is magnesium?
8.3% for the anhydrous salt (24.305 ÷ 294.495) and 7.8% for the monohydrate (24.305 ÷ 312.510). EFSA's 2024 opinion reports 7.5% to 8.8% in batches of the monohydrate ingredient, so "about 7 to 8%" is a fair summary.
Does a higher magnesium percentage tell you which form to choose?
No. The percentage describes weight only, not how a form is absorbed or what a serving costs. Our oxide vs citrate vs glycinate guide reports what NIH and the NHS say on those questions. The three forms and pack sizes are on the Tri-Mag Night capsule page, and the FAQ covers delivery and returns.
How we checked this page
- Sources opened. On 10 October 2026 we read PubChem records for every compound (CIDs under Sources), the CIAAW atomic weights, EFSA's 2024 opinion on magnesium L-threonate, Regulation (EC) No 1170/2009 and the NIH ODS magnesium fact sheet (read through an Internet Archive copy of 7 October 2026, as NIH's server refused our automated request). Our molar masses are our own sums and agree with PubChem to within 0.03 g/mol.
- What we could not find. A regulator's table of magnesium share by compound, a rule saying which compound a bare "magnesium citrate" means on a label, and printed hydration states on most labels.
- Review. No doctor, pharmacist or dietitian has reviewed this page.
- Who we are. Satiovex products are sold by Xinop LLC, trading as Satiovex. We run this site and have a financial interest in the products.
- Corrections. If something here is wrong, contact us and we will check it.
Last updated 10 October 2026 by the Satiovex editorial team.
Sources
- PubChem compound records: CID 14792, 73981, 11029, 6099959, 8949, 53249332, 164748, 6536825, 84645, 24644, 24843, 5360315, 24083, 13343447, 45489777 and 76963881.
- CIAAW, Abridged Standard Atomic Weights (2024 table).
- EFSA Panel on Nutrition, Novel Foods and Food Allergens, opinion on magnesium L-threonate as a novel food (EFSA Journal 2024;22(3):e8656).
- Commission Regulation (EC) No 1170/2009, Annex II (EUR-Lex).
- NIH Office of Dietary Supplements, Magnesium: Fact Sheet for Health Professionals (updated 6 January 2026).