Label arithmetic · NIH DSLD snapshot 2026-08-10
How much magnesium is in magnesium oxide? 60.3% by weight, so 100 mg of magnesium takes 166 mg of oxide
60.3% of magnesium oxide is magnesium: 100 mg takes 166 mg of salt, 0.2 size 00 capsules. From $0.0148 per 100 mg; 61 labels inside.
Magnesium oxide is 60.3% elemental magnesium, so 100 mg of magnesium needs 166 mg of compound, about 0.2 size 00 capsules at 0.8 g/mL powder density. 0 of 12 capsule labels naming oxide alone exceed size 000. Cheapest by declared elemental magnesium among 5 ranked offers is $0.0148 per 100 mg; median $0.0293; prices observed 2026-10-26 to 2026-11-02.
computed from chemical formula
Chart data
| Displayed chart text |
|---|
| oxide |
| 60.3% |
| hydroxide |
| 41.7% |
| carbonate |
| 24.8–28.8% |
| chloride |
| 12.0–25.5% |
| sulfate |
| 9.9–20.2% |
| citrate |
| 11.3–16.2% |
| aspartate |
| 7.5–15.6% |
| malate |
| 12.6–15.5% |
| glycinate |
| 11.8–14.1% |
| glycerophosphate |
| 12.5% |
| lactate |
| 10.2–12.0% |
| taurate |
| 8.9% |
| L-threonate |
| 8.3% |
| orotate |
| 7.3% |
| gluconate |
| 5.9% |
Data release 2026-08-10-f441aa9f · registry snapshot 2026-08-10 · latest price observation 2026-11-02 · chemistry 2026-10-17
Recompute for your bottle
Enter your container price, declared elemental amount and servings to calculate a price per 100 mg for this bottle.
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How much elemental magnesium is actually in 100, 200 or 400 mg of oxide?
Magnesium oxide is 60.3% elemental magnesium by mass (MgO, molar mass 40.3). Magnesium oxide has a molar mass of 40.3 against magnesium's 24.305, so 60.3% of its mass is magnesium. Every 100 mg of elemental magnesium from it needs 166 mg of the compound, calculated 2026-10-17.
computedThis defined salt has one calculated elemental fraction from its formula.
Chart data
| Displayed chart text |
|---|
| oxide |
| 663 |
| Elemental magnesium | oxide required | Size 00 capsules that much powder fills |
|---|---|---|
| 100 mg | 166 mg | 1 size 00 capsules (0.2 capsules' worth of powder) |
| 200 mg | 332 mg | 1 size 00 capsules (0.5 capsules' worth of powder) |
| 400 mg | 663 mg | 1 size 00 capsules (0.9 capsules' worth of powder) |
Source · Chemical formula and atomic masses · Calculated 2026-08-10; powder density 0.8 g/mL, the top of the usual 0.6–0.8 range · release 2026-08-10-f441aa9f · CSV · method
Estimated salt mass versus assumed capsule capacity
0 of 12 capsule labels naming oxide alone are above the assumed size 000 capacity at powder density 0.8 g/mL, against 8 of 137 capsule labels across the audited registry. 11 fit size 0 or 00 and 1 need size 000. This is computed with a stated assumption of powder density 0.8 g/mL, the top of the usual 0.6–0.8 range and the most favorable mass per capsule.
computed with assumption12 capsule labels naming oxide alone can be checked against capsule sizes.
Chart data
| Displayed chart text |
|---|
| oxide |
| fits 11 of 12 |
| needs 000 1 of 12 |
| exceeds 0 of 12 |
| all audited |
| fits 82 of 137 |
| needs 000 47 of 137 |
| exceeds 8 of 137 |
| Mass budget verdict | Labels |
|---|---|
| Fits size 0 or 00 | 11 of 12 |
| Needs size 000 | 1 of 12 |
| Exceeds size 000 | 0 of 12 |
A size 00 capsule holds about 730 mg of powder at powder density 0.8 g/mL, the top of the usual 0.6–0.8 range; a size 000 about 1,100 mg.
Source · NIH DSLD labels; mass balance · Recognized salt only; 2026-08-10 · release 2026-08-10-f441aa9f · CSV · method
Is a label called oxide really oxide, or mixed with another salt?
0 of 61 labels naming oxide also name another form as of 2026-08-10. The table counts partner names on filed labels; a named blend does not establish the elemental contribution of each salt. Naming one salt is not the same as fitting it: 0 of 12 capsule labels naming oxide alone exceed size 000. Open the full label list to inspect individual records.
measuredA defined molecular formula permits a calculated fraction.
| Other named form | Labels |
|---|---|
| No other named form | 61 labels reviewed |
Source · NIH DSLD magnesium rows · Labels naming this salt; 2026-08-10 · release 2026-08-10-f441aa9f · CSV · method
I need 200 mg of actual magnesium. What changes in compound weight and capsules between oxide and other forms?
For 200 mg of elemental magnesium, oxide needs 332 mg of compound, against oxide at 332 mg. Size 00 holds about 730 mg at powder density 0.8 g/mL, the top of the usual 0.6–0.8 range. Each row uses the stated elemental fraction; hydration ambiguity stays a range, and any price comparison remains within a single salt.
computed with assumption| Salt | Elemental fraction | Compound for 200 mg | Size 00 capsules |
|---|---|---|---|
| Magnesium oxide | 60.3% | 332 mg | 1 size 00 |
| Magnesium glycinate | 11.8–14.1% | 1,418–1,691 mg | 2–3 size 00 |
| Magnesium citrate | 11.3–16.2% | 1,238–1,770 mg | 2–3 size 00 |
| Magnesium malate | 12.6–15.5% | 1,287–1,584 mg | 2–3 size 00 |
Source · Chemical formulas and capsule capacity · Calculated 2026-08-10; powder density 0.8 g/mL, the top of the usual 0.6–0.8 range · release 2026-08-10-f441aa9f · CSV · method
What does oxide cost per 100 mg of elemental magnesium, and which label is cheapest by declared elemental magnesium?
Cheapest by declared elemental magnesium among 5 ranked offers is $0.0148 per 100 mg; median $0.0293; prices observed 2026-10-26 to 2026-11-02. One offer means one ASIN and observation date; 2 observations are on review; their pack or dose has not passed the match checks. The ranked price uses the label's declared elemental amount.
computed5 unique offers have a ranked price per reference amount of declared elemental magnesium.
Chart data
| Displayed chart text |
|---|
| n=5 |
| P25 $0.0258 |
| P75 $0.0356 |
| median $0.0293 |
| Rank | Label | EC100 | Match and observation |
|---|---|---|---|
| 1 | Nutricost Magnesium Oxide | $0.0148 per 100 mg | confirmed; 2026-11-02 · $14.95 for 240 units |
| 2 | tnvitamins Magnesium Oxide 420 mg | $0.0258 per 100 mg | confirmed; 2026-11-02 · $12.99 for 120 units |
| 3 | Douglas Laboratories Magnesium Oxide | $0.0293 per 100 mg | confirmed; 2026-11-02 · $22.00 for 250 units |
| 4 | Wonder Labs Magnesium Oxide 400 | $0.0356 per 100 mg | confirmed; 2026-11-02 · $21.49 for 250 units |
| 5 | Carlson Magnesium Gels 400 mg | $0.0636 per 100 mg | verified; 2026-11-02 · $25.42 for 100 units |
| On review | BulkSupplements.com Magnesium Oxide Powder | No ranked EC100 | pack weight differs: the offer lists 250 g, the label 500 g; 2026-09-11 |
| On review | NusaPure Magnesium Oxide 1000 mg | No ranked EC100 | the filed elemental amount (1000 mg per serving) is likely the compound mass; 2026-09-21 |
Verified: a row matched to the label by hand in August 2026 that passes every automatic check. Confirmed: brand, salt and dose match the label in the September 2026 check. Only these two are ranked; rows on review are not.
Source · Amazon via licensed data provider · Unique ASIN and observation date; prices observed 2026-10-26 to 2026-11-02 · release 2026-08-10-f441aa9f · CSV · method
What else is in oxide labels, including stearate, shells and fillers?
8 named excipients appear in the top displayed list among 61 labels naming oxide as of 2026-08-10. A listed ingredient is a filed name, not a quantified mass; open the underlying label to check context and capsule material.
measured
Chart data
| Displayed chart text |
|---|
| magnesium stearate |
| 30 |
| cellulose |
| 27 |
| silicon dioxide |
| 22 |
| microcrystalline cellulose |
| 19 |
| stearic acid |
| 14 |
| dicalcium phosphate |
| 13 |
| gelatin |
| 11 |
| croscarmellose sodium |
| 7 |
| microcrystalline |
| Filed ingredient | Labels |
|---|---|
| magnesium stearate | 30 of 61 |
| cellulose | 27 of 61 |
| silicon dioxide | 22 of 61 |
| microcrystalline cellulose | 19 of 61 |
| stearic acid | 14 of 61 |
| dicalcium phosphate | 13 of 61 |
| gelatin | 11 of 61 |
| croscarmellose sodium | 7 of 61 |
Source · NIH DSLD full label ingredient fields · Labels naming this salt; 2026-08-10 · release 2026-08-10-f441aa9f · CSV · method
What did studies measure about absorption and side effects for oxide?
12 studies in our PubMed checked registry measured outcomes involving oxide as of 2026-08-10. The table names each design and measured outcome, against no pooled comparison across different study methods. 2 records mention gastrointestinal or other adverse outcomes.
measured12 studies in this registry measured outcomes involving oxide.
| Year | Study design and measured outcome | PubMed |
|---|---|---|
| 2026 | Randomized, open-label pharmacokinetic study in 24 healthy male volunteers aged 18-45 years, equally assigned to a single oral dose of either 750 mg or 2000 mg magnesium oxide. Serum magnesium concentrations at baseline and multiple time points up to 12 hours post-dose (colorimetric assay); pharmacokinetic parameters Cmax, Tmax, and AUC0-12 via non-compartmental analysis; safety via vital signs, laboratory parameters, ECG, and adverse events. | PMID 42091979 |
| 2024 | Double-blind, randomized, cross-over clinical study in 40 healthy women and men. Participants followed a low-magnesium diet for 7 days and fasted 8 hours, then received a single oral dose of each of four products in cross-over fashion: microencapsulated magnesium (Mg-MS / MAGSHAPE), magnesium oxide (MgO), magnesium citrate (Mg-C), and magnesium bisglycinate (Mg-BG). Blood was drawn by digital puncture before dosing (0 h) and at 1, 4, and 6 hours after each product. Plasma magnesium concentration at 0, 1, 4, and 6 hours after oral intake of each of the four products; gastrointestinal side effects (intestinal motility, sensations of gastric heaviness) associated with each product. | PMID 39770988 |
| 2022 | Short-term, 10-day supplementation study in 61 healthy young female adults, comparing three magnesium supplement forms: magnesium oxide (powder/granulate), magnesium citrate, and magnesium carbonate (effervescent tablets). Ionized magnesium concentration and its percentage of total magnesium; serum total magnesium concentration; other serum electrolyte levels , each assessed at baseline and after the 10-day intervention. | PMID 35041150 |
| 2020 | Absorption of several magnesium compounds profiled across doses rather than at a single dose. Absorption is treated as dose-dependent, so a comparison made at one dose need not hold at another , which is why single-dose head-to-head results disagree. | PMID 30761462 |
| 2019 | Single-dose administration of 400 mg/70 kg magnesium as one of five compounds (magnesium sulfate, magnesium oxide, magnesium acetyl taurate, magnesium citrate, magnesium malate) to Sprague Dawley rats, with a control group, followed by time-dependent tissue and serum sampling. Time-dependent magnesium absorption profile (area under the curve) in serum; magnesium tissue penetration and concentration, including brain tissue; behavioral indicators (e.g., anxiety-related behavior) recorded in the animals. | PMID 29679349 |
| 2012 | Oral magnesium citrate versus magnesium oxide in healthy subjects; intracellular magnesium measured by X-ray dispersion analysis, alongside platelet function. The comparison used intracellular magnesium rather than serum magnesium, which changes what the read-out means. | PMID 22433473 |
| 2005 | Eighty male Wistar rats fed a magnesium-depleted diet for three weeks, then randomised into ten groups, each receiving a different magnesium salt labelled with a stable isotope. Stable isotopes allow absorption and retention to be traced directly rather than inferred from urine, across ten salts at once , the widest head-to-head comparison in the literature. | PMID 16548135 |
| 2003 | Randomised, double-blind, placebo-controlled parallel study in 46 healthy individuals, 300 mg of elemental magnesium per day, comparing an amino-acid chelate, citrate and oxide. Relative bioavailability of the three preparations was compared at an equal elemental dose. | PMID 14596323 |
4 additional rows
| Year | Study design and measured outcome | PubMed |
|---|---|---|
| 2001 | Four commercially available US preparations given to healthy volunteers; bioavailability measured as the increment in urinary magnesium excretion. The study set out to test the claim that organic magnesium salts are more easily absorbed than inorganic ones, using urinary excretion as the read-out. | PMID 11794633 |
| 1995 | Comparison of magnesium diglycinate (a chelate) with magnesium oxide in patients who had undergone ileal resection. The work followed in vitro and in situ findings suggesting diglycinate is absorbed by a different route than inorganic salts, and tested that in patients with impaired absorption. | PMID 7815675 |
| 1990 | In vitro solubility of 25 mmol of each salt across hydrochloric acid concentrations mimicking achlorhydric to peak acid secretion, plus in vivo gastrointestinal absorbability. Magnesium oxide was virtually insoluble across the acid range tested, while citrate dissolved; absorbability was then compared in vivo. | PMID 2407766 |
| 1990 | Seven normal subjects and four patients with recurrent calcium oxalate stones; 486 mg of magnesium per day for two weeks, taken on an empty stomach and again with food. Taken on an empty stomach, urinary magnesium rose by only 77–79 mg per day out of 486 mg given , and the increase changed when the dose was taken with food. | PMID 2299712 |
Source · PubMed checked study registry · Registry checked 2026-08-10 · release 2026-08-10-f441aa9f · CSV · method
Which labels file oxide, and how much do they declare per serving?
61 labels name oxide; 59 have a computable elemental amount per serving, with median 400 mg, against the full list linked below. The first eight are shown here. Values are filed elemental magnesium, not an assay of the contents, in the NIH DSLD snapshot 2026-08-10.
measured
Chart data
| Displayed chart text |
|---|
| P10 241 mg |
| P50 400 mg |
| P90 500 mg |
| Label | Declared elemental per serving | NIH DSLD |
|---|---|---|
| Basic Vitamins Magnesium 250 mg | 250 mg | 250165 |
| BulkSupplements.com Magnesium Oxide Powder | 500 mg | 329720 |
| Carlson Magnesium Gels 400 mg | 400 mg | 216334 |
| Carlson Magnesium Gels 400 mg | 400 mg | 216338 |
| DC Magnesium 500 mg | 500 mg | 245144 |
| DC Magnesium 500 mg | 500 mg | 267036 |
| DC Magnesium 500 mg | 500 mg | 267037 |
| DC Magnesium Oxide 400 mg | 241 mg | 265891 |
Source · NIH DSLD on-market labels · Labels naming this salt; snapshot 2026-08-10 · release 2026-08-10-f441aa9f · CSV · method
Where do these numbers come from, and how do I cite or correct them?
The 61 recognized oxide labels come from the NIH DSLD snapshot 2026-08-10. Chemistry was calculated from molecular formulas on 2026-10-17; observed retail prices are checked 2026-11-02. The linked CSV carries only values displayed on this page. Cite the release and report a claim if a filed label or calculation needs correction.
computed| Layer | Source and date |
|---|---|
| Labels | NIH DSLD snapshot 2026-08-10 |
| Chemistry | Formula calculation 2026-10-17 |
| Retail | Prices observed 2026-10-26 to 2026-11-02 |
Source · NIH DSLD; chemical formulas; Amazon via licensed data provider · Release 2026-08-10-f441aa9f · release 2026-08-10-f441aa9f · CSV · method