Same elemental magnesium · two salts · snapshot 2026-08-10

Magnesium chloride vs hydroxide: 783–1,672 vs 480 mg of compound for 200 mg of magnesium

Magnesium chloride is 12.0–25.5% elemental magnesium and magnesium hydroxide is 41.7%, so 200 mg of magnesium needs 783–1,672 mg of chloride against 480 mg of hydroxide: 2–3 vs 1 size 00 capsules at powder density 0.8 g/mL, the top of the usual 0.6–0.8 range. No capsule label names either salt alone as of 2026-08-10, so no capsule verdict is counted. Neither salt has a ranked US retail price as of 2026-11-02.

computed from chemical formulas

chloride for 200 mg Mg783–1,672 mg12.0–25.5% magnesium · 2–3 size 00

hydroxide for 200 mg Mg480 mg41.7% magnesium · 1 size 00

Exceeds size 000none · nonechloride · hydroxide capsule labels

Cheapest by declared elemental magnesium, per 100 mg, within each saltchloride none · hydroxide none0 and 0 ranked offers · 2026-11-02

Compound mass for the same elemental magnesium: dark dot hydroxide (41.7%), grey dot chloride (12.0–25.5%, upper mass bound); the labels give each salt's full range.

Chart data

Chart labels and values for the main chart
Displayed chart text
100 mg magnesium
hydroxide 240 · chloride 392–836
200 mg magnesium
hydroxide 480 · chloride 783–1,672
400 mg magnesium
hydroxide 960 · chloride 1,567–3,344

Data release 2026-08-10-f441aa9f · registry snapshot 2026-08-10 · latest price observation 2026-11-02 · chemistry 2026-10-17

Elemental: The magnesium itself; the rest of the compound weight is the partner molecule.

Compound: The whole salt that must physically fit in a capsule; a lower magnesium fraction means more compound for the same magnesium.

How much chloride or hydroxide carries the same elemental magnesium?

At the same elemental amount, hydroxide (41.7% magnesium) always needs less compound than chloride (12.0–25.5%): for 400 mg of magnesium, 960 mg against 1,567–3,344 mg. That is the mass of powder per dose; how much of it is absorbed is what the studies below measured.

computed

Compound mass and size 00 capsules for chloride and hydroxide
Elemental magnesium	chloride compound	chloride size 00	hydroxide compound	hydroxide size 00
100 mg	392–836 mg	1–2	240 mg	1
200 mg	783–1,672 mg	2–3	480 mg	1
400 mg	1,567–3,344 mg	3–5	960 mg	2

chloride: anhydrous 25.5%, hexahydrate 12.0%; hydration ambiguity stays a range.

Source · Chemical formulas and NIH DSLD labels · snapshot 2026-08-10 · release 2026-08-10-f441aa9f · CSV · method

Estimated salt mass versus assumed capsule capacity

No capsule label names either salt alone as of 2026-08-10, so no capsule verdict is counted. Verdicts use the most favourable hydration and the most units per serving at powder density 0.8 g/mL, the top of the usual 0.6–0.8 range; the audited registry as a whole has 8 of 137 capsule labels above size 000.

computed with assumption

Capsule verdicts for chloride and hydroxide labels
Salt	Audited capsule labels	Fits 0 or 00	Needs 000	Exceeds 000
chloride	0	0	0	0
hydroxide	0	0	0	0

Source · NIH DSLD labels; mass balance · recognized salt only; snapshot 2026-08-10 · release 2026-08-10-f441aa9f · CSV · method

What does each cost per 100 mg of elemental magnesium, within its own salt?

No ranked US retail price is matched for either salt as of 2026-11-02.

computed

Price per 100 mg of declared elemental magnesium, within each salt
Salt	Ranked offers	Lowest per 100 mg	Median per 100 mg	Observed
chloride	0	none	none	2026-11-02
hydroxide	0	none	none	2026-11-02

Source · Amazon via licensed data provider; NIH DSLD · unique ASIN × date; prices observed 2026-10-26 to 2026-11-02 · release 2026-08-10-f441aa9f · CSV · method

Has any study measured chloride and hydroxide side by side?

No study in the PubMed-checked registry measured chloride and hydroxide side by side as of 2026-08-10; 3 involve chloride and 1 involve hydroxide separately.

measured

Registry studies involving chloride or hydroxide
Year	Study	Salts measured	PubMed
2005	Study of magnesium bioavailability from ten organic and inorganic Mg salts in Mg-depleted rats using a stable isotope approach	oxide, chloride, sulfate, carbonate, citrate, gluconate, lactate, aspartate, glycinate	16548135
2001	Bioavailability of US commercial magnesium preparations	oxide, chloride, lactate, aspartate	11794633
1992	Blood and urinary magnesium kinetics after oral magnesium supplements.	chloride, gluconate	1468087
2025	Comparing the Bioavailability of Two Seawater-Derived Magnesium Preparations.	citrate, hydroxide	40955524

Source · PubMed-checked study registry · registry checked 2026-08-10 · release 2026-08-10-f441aa9f · CSV · method

How many labels name both chloride and hydroxide?

No label names both chloride and hydroxide as of 2026-08-10, against 19 labels naming chloride and 10 naming hydroxide.

measured

Labels naming both salts
Label	Declared elemental per serving	NIH DSLD
No label as of 2026-08-10

Source · Chemical formulas and NIH DSLD labels · snapshot 2026-08-10 · release 2026-08-10-f441aa9f · CSV · method

What does every dose from 25 to 1,000 mg of magnesium need in each salt?

The table converts 40 elemental amounts, 25 to 1,000 mg in 25 mg steps, into compound mass and size 00 capsules for both salts, against 730 mg per size 00 capsule at powder density 0.8 g/mL, the top of the usual 0.6–0.8 range. The first eight rows are shown; the rest open below.

computed

Compound mass reference, 25 to 1,000 mg of elemental magnesium
Elemental magnesium	chloride compound	chloride size 00	hydroxide compound	hydroxide size 00
25 mg	98–209 mg	1	60 mg	1
50 mg	196–418 mg	1	120 mg	1
75 mg	294–627 mg	1	180 mg	1
100 mg	392–836 mg	1–2	240 mg	1
125 mg	490–1,045 mg	1–2	300 mg	1
150 mg	588–1,254 mg	1–2	360 mg	1
175 mg	685–1,463 mg	1–3	420 mg	1
200 mg	783–1,672 mg	2–3	480 mg	1

32 additional rows

Compound mass reference, 25 to 1,000 mg of elemental magnesium, additional rows
Elemental magnesium	chloride compound	chloride size 00	hydroxide compound	hydroxide size 00
225 mg	881–1,881 mg	2–3	540 mg	1
250 mg	979–2,090 mg	2–3	600 mg	1
275 mg	1,077–2,299 mg	2–4	660 mg	1
300 mg	1,175–2,508 mg	2–4	720 mg	1
325 mg	1,273–2,717 mg	2–4	780 mg	2
350 mg	1,371–2,926 mg	2–5	840 mg	2
375 mg	1,469–3,135 mg	3–5	900 mg	2
400 mg	1,567–3,344 mg	3–5	960 mg	2
425 mg	1,665–3,554 mg	3–5	1,020 mg	2
450 mg	1,763–3,763 mg	3–6	1,080 mg	2
475 mg	1,861–3,972 mg	3–6	1,140 mg	2
500 mg	1,958–4,181 mg	3–6	1,200 mg	2
525 mg	2,056–4,390 mg	3–7	1,260 mg	2
550 mg	2,154–4,599 mg	3–7	1,320 mg	2
575 mg	2,252–4,808 mg	4–7	1,380 mg	2
600 mg	2,350–5,017 mg	4–7	1,440 mg	2
625 mg	2,448–5,226 mg	4–8	1,500 mg	3
650 mg	2,546–5,435 mg	4–8	1,560 mg	3
675 mg	2,644–5,644 mg	4–8	1,619 mg	3
700 mg	2,742–5,853 mg	4–9	1,679 mg	3
725 mg	2,840–6,062 mg	4–9	1,739 mg	3
750 mg	2,938–6,271 mg	5–9	1,799 mg	3
775 mg	3,036–6,480 mg	5–9	1,859 mg	3
800 mg	3,134–6,689 mg	5–10	1,919 mg	3
825 mg	3,231–6,898 mg	5–10	1,979 mg	3
850 mg	3,329–7,107 mg	5–10	2,039 mg	3
875 mg	3,427–7,316 mg	5–11	2,099 mg	3
900 mg	3,525–7,525 mg	5–11	2,159 mg	3
925 mg	3,623–7,734 mg	5–11	2,219 mg	4
950 mg	3,721–7,943 mg	6–11	2,279 mg	4
975 mg	3,819–8,152 mg	6–12	2,339 mg	4
1,000 mg	3,917–8,361 mg	6–12	2,399 mg	4

Source · Chemical formulas and NIH DSLD labels · snapshot 2026-08-10 · release 2026-08-10-f441aa9f · CSV · method