Best Magnesium Oxide
The best magnesium oxide we track, ranked by real cost-per-dose — not paid placements. Across 11 brands, 2 are third-party tested in a public registry.
Updated October 2026prices checked what’s changed
How much does Magnesium Oxide cost?
Magnesium Oxide costs a median $0.08 per serving — the cheapest of the 16 we can price per dose is $0.03 per serving, or $0.02/day to reach the commonly-studied 300 mg dose. Prices checked October 2026.
Ranked across 16 products · prices checked Oct 10, 2026
How we rank
We rank by cost-per-dose — price ÷ servings, normalized to the daily dose (300 mg/day) — so bottle sizes and strengths compare fairly. Prices are scraped at publication and re-checked when the catalog refreshes (see the “Prices checked” stamp above). There is no paid placement and no kickback for ordering. Full methodology · Editorial standards.
When cheapest ≠ best value
Our cheapest magnesium oxide per dose is an oxide form — cheap and concentrated, but a low-absorption form, so your body takes up relatively little of it. Chelated forms (e.g. glycinate, citrate) are absorbed far better, so compare cost per absorbed unit, not sticker price alone. A bigger bottle isn’t automatically cheaper per dose either — this list already ranks by cost per dose, so a larger count only wins if it truly costs less per serving. Compare Magnesium Oxide forms.
Our data on this: how much the big bottle saves per serving · the gummy tax · the form premium · the price spread.
Full ranking by cost per dose
Cost-per-serving normalizes price across bottle sizes — a 60-count and a 365-count compare fairly.
- See offer#1Best valueMagnesium Oxide 400mg, 500 Capsules | Elemental Form…
capsule · 400mg · 500 servings · $15.19
$0.03per serving$0.02 / 300 mg - See offer$0.03per serving1.1× #1$0.04 / 300 mg
- See offer$0.04per serving1.2× #1$0.03 / 300 mg
- See offer$0.04per serving1.3× #1$0.03 / 300 mg
- See offer$0.05per serving1.6× #1$0.04 / 300 mg
- See offer$0.05per serving1.7× #1$0.04 / 300 mg
- See offer$0.06per serving2.1× #1
- See offer$0.07per serving2.5× #1$0.06 / 300 mg
- See offer$0.08per serving2.7× #1$0.05 / 300 mg
- See offer$0.10per serving3.4× #1$0.06 / 300 mg
- See offer$0.11per serving3.5× #1$0.07 / 300 mg
- See offer$0.14per serving4.5× #1$0.10 / 300 mg
- See offer$0.14per serving4.7× #1$0.11 / 300 mg
- See offer$0.17per serving5.5× #1$0.13 / 300 mg
- See offer#15Sports Research® Magnesium Oxide 420mg w/Coconut MCT Oil
softgel · 420mg · 90 servings · $16.95
Informed Choice$0.19per serving6.2× #1$0.13 / 300 mg - See offer$0.37per serving12.1× #1$0.27 / 300 mg
See also: Magnesium Oxide basics · all best-value rankings
Read: Magnesium Oxide guides
Related comparisons, stacks & nutrients
Magnesium Oxide brands we compare — which are third-party tested?
2 of the 11 brands ranked above appear in an independent certifier's own public registry. A certification confirms the label matches the contents — it says nothing about how well the supplement works, and an uncertified brand is not automatically worse.
Frequently asked
How much does Magnesium Oxide cost?+
The cheapest magnesium oxide we track is $0.03 per serving ($15.19 for 500 servings), against a typical $0.08 per serving across the 16 we can price per dose — about $0.91 a month at the cheapest. That's real cost per dose from live Amazon US prices as of October 2026, not the sticker price.
What is the best-value Magnesium Oxide supplement?+
Magnesium Oxide 400mg, 500 Capsules | Elemental Form for Max Concentration… — $0.03 per serving ($15.19 for 500 servings), the lowest cost-per-dose magnesium oxide in our Amazon US catalog as of October 2026.
How much does Magnesium Oxide cost per day?+
The cheapest magnesium oxide we track works out to $0.03 per serving, against a typical $0.08 per serving across the 16 we can price per dose; to reach the commonly-studied 300 mg/day dose the cheapest is $0.02/day. Retailers and review sites list a price and a serving size but rarely divide it out — this is what a day actually costs, as of October 2026.
What is the typical cost per dose for Magnesium Oxide?+
About $0.08 per serving across the 16 magnesium oxide products we can price per dose (combination products are left out — their single label dose belongs to whichever ingredient the product is built around) — the cheapest we track is $0.03 per serving, with most falling between $0.05 and $0.14.
What's the cheapest effective Magnesium Oxide?+
To reach the commonly-studied 300 mg/day dose, Magnesium Oxide 400mg, 500 Capsules | Elemental Form for Max… is the best value at $0.02 per day — cheaper than bottles that look low-priced per serving but are underdosed.
What is the highest-quality Magnesium Oxide supplement?+
Of the 11 magnesium oxide brands ranked here, 2 hold a third-party certification we could verify in a public registry: Nature Made (USP Verified), Sports Research (Informed Choice). Certification means an independent lab confirmed the label matches the contents and screened for contaminants — it does not rate how well the supplement works. The cheapest certified option is Nature Made Magnesium Oxide 250 mg at $0.03 per serving.
Which Magnesium Oxide brands are third-party tested?+
Nature Made — USP Verified; Sports Research — Informed Choice. We only count a brand as tested when it appears in the certifier's own public registry (USP Verified, NSF Certified for Sport, Informed Choice), never on a claim printed on the label. The remaining 9 brands on this page have no certification we could verify.
Which Magnesium Oxide is the top rated?+
We don't republish marketplace star ratings — they belong to the retailer, they move constantly, and a 4.6 average tells you nothing about what is in the capsule. The two things you can verify are what a dose costs and whether an independent lab checked the label. On both counts, Nature Made Magnesium Oxide 250 mg stands out: USP Verified certified at $0.03 per serving.
Independent testing
2 of 11 tracked Magnesium Oxide brands here are flagged as carrying independent third-party testing — a voluntary check of a product's identity, potency and contaminants by an outside lab. It's a quality signal, not a value or efficacy claim. Confirm any brand's current status on the official registries:
Testing status is self-reported by the brand or drawn from public certification and may change — always verify on the official registry before purchase.
References & sources
We link primary sources and paraphrase their findings — never copy their text, tables, or images. Cost-per-dose figures are our own first-party catalog data.