Same elemental magnesium · two salts · snapshot 2026-08-10
Magnesium carbonate vs sulfate: 694–807 vs 991–2,028 mg of compound for 200 mg of magnesium
Magnesium carbonate is 24.8–28.8% elemental magnesium and magnesium sulfate is 9.9–20.2%, so 200 mg of magnesium needs 694–807 mg of carbonate against 991–2,028 mg of sulfate: 1–2 vs 2–3 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
Chart data
| Displayed chart text |
|---|
| 100 mg magnesium |
| carbonate 347–404 · sulfate 495–1,014 |
| 200 mg magnesium |
| carbonate 694–807 · sulfate 991–2,028 |
| 400 mg magnesium |
| carbonate 1,387–1,614 · sulfate 1,981–4,057 |
Data release 2026-08-10-f441aa9f · registry snapshot 2026-08-10 · latest price observation 2026-11-02 · chemistry 2026-10-17
How much carbonate or sulfate carries the same elemental magnesium?
At the same elemental amount, carbonate (24.8–28.8% magnesium) always needs less compound than sulfate (9.9–20.2%): for 400 mg of magnesium, 1,387–1,614 mg against 1,981–4,057 mg. That is the mass of powder per dose; how much of it is absorbed is what the studies below measured.
computed| Elemental magnesium | carbonate compound | carbonate size 00 | sulfate compound | sulfate size 00 |
|---|---|---|---|---|
| 100 mg | 347–404 mg | 1 | 495–1,014 mg | 1–2 |
| 200 mg | 694–807 mg | 1–2 | 991–2,028 mg | 2–3 |
| 400 mg | 1,387–1,614 mg | 2–3 | 1,981–4,057 mg | 3–6 |
carbonate: anhydrous or hydrated; labels rarely state which; sulfate: anhydrous 20.2%, heptahydrate 9.9%; 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| Salt | Audited capsule labels | Fits 0 or 00 | Needs 000 | Exceeds 000 |
|---|---|---|---|---|
| carbonate | 0 | 0 | 0 | 0 |
| sulfate | 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| Salt | Ranked offers | Lowest per 100 mg | Median per 100 mg | Observed |
|---|---|---|---|---|
| carbonate | 0 | none | none | 2026-11-02 |
| sulfate | 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 carbonate and sulfate side by side?
One study in the PubMed-checked registry measured both salts in the same design; 2 involve carbonate and 2 involve sulfate in total. They measured outcomes of the salts, not of any label.
measured| 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 |
| 2022 | Effects of short-term magnesium supplementation on ionized, total magnesium and other relevant electrolytes levels. | oxide, citrate, carbonate | 35041150 |
| 2019 | Timeline (Bioavailability) of Magnesium Compounds in Hours: Which Magnesium Compound Works Best? | sulfate, oxide, taurate, citrate, malate | 29679349 |
Source · PubMed-checked study registry · registry checked 2026-08-10 · release 2026-08-10-f441aa9f · CSV · method
How many labels name both carbonate and sulfate?
No label names both carbonate and sulfate as of 2026-08-10, against 23 labels naming carbonate and 4 naming sulfate.
measured| 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| Elemental magnesium | carbonate compound | carbonate size 00 | sulfate compound | sulfate size 00 |
|---|---|---|---|---|
| 25 mg | 87–101 mg | 1 | 124–254 mg | 1 |
| 50 mg | 173–202 mg | 1 | 248–507 mg | 1 |
| 75 mg | 260–303 mg | 1 | 371–761 mg | 1–2 |
| 100 mg | 347–404 mg | 1 | 495–1,014 mg | 1–2 |
| 125 mg | 434–504 mg | 1 | 619–1,268 mg | 1–2 |
| 150 mg | 520–605 mg | 1 | 743–1,521 mg | 2–3 |
| 175 mg | 607–706 mg | 1 | 867–1,775 mg | 2–3 |
| 200 mg | 694–807 mg | 1–2 | 991–2,028 mg | 2–3 |
32 additional rows
| Elemental magnesium | carbonate compound | carbonate size 00 | sulfate compound | sulfate size 00 |
|---|---|---|---|---|
| 225 mg | 780–908 mg | 2 | 1,114–2,282 mg | 2–4 |
| 250 mg | 867–1,009 mg | 2 | 1,238–2,535 mg | 2–4 |
| 275 mg | 954–1,110 mg | 2 | 1,362–2,789 mg | 2–4 |
| 300 mg | 1,041–1,211 mg | 2 | 1,486–3,043 mg | 3–5 |
| 325 mg | 1,127–1,312 mg | 2 | 1,610–3,296 mg | 3–5 |
| 350 mg | 1,214–1,412 mg | 2 | 1,734–3,550 mg | 3–5 |
| 375 mg | 1,301–1,513 mg | 2–3 | 1,857–3,803 mg | 3–6 |
| 400 mg | 1,387–1,614 mg | 2–3 | 1,981–4,057 mg | 3–6 |
| 425 mg | 1,474–1,715 mg | 3 | 2,105–4,310 mg | 3–6 |
| 450 mg | 1,561–1,816 mg | 3 | 2,229–4,564 mg | 4–7 |
| 475 mg | 1,648–1,917 mg | 3 | 2,353–4,817 mg | 4–7 |
| 500 mg | 1,734–2,018 mg | 3 | 2,476–5,071 mg | 4–7 |
| 525 mg | 1,821–2,119 mg | 3 | 2,600–5,325 mg | 4–8 |
| 550 mg | 1,908–2,220 mg | 3–4 | 2,724–5,578 mg | 4–8 |
| 575 mg | 1,994–2,320 mg | 3–4 | 2,848–5,832 mg | 4–8 |
| 600 mg | 2,081–2,421 mg | 3–4 | 2,972–6,085 mg | 5–9 |
| 625 mg | 2,168–2,522 mg | 3–4 | 3,096–6,339 mg | 5–9 |
| 650 mg | 2,255–2,623 mg | 4 | 3,219–6,592 mg | 5–10 |
| 675 mg | 2,341–2,724 mg | 4 | 3,343–6,846 mg | 5–10 |
| 700 mg | 2,428–2,825 mg | 4 | 3,467–7,099 mg | 5–10 |
| 725 mg | 2,515–2,926 mg | 4–5 | 3,591–7,353 mg | 5–11 |
| 750 mg | 2,601–3,027 mg | 4–5 | 3,715–7,606 mg | 6–11 |
| 775 mg | 2,688–3,128 mg | 4–5 | 3,839–7,860 mg | 6–11 |
| 800 mg | 2,775–3,228 mg | 4–5 | 3,962–8,114 mg | 6–12 |
| 825 mg | 2,862–3,329 mg | 4–5 | 4,086–8,367 mg | 6–12 |
| 850 mg | 2,948–3,430 mg | 5 | 4,210–8,621 mg | 6–12 |
| 875 mg | 3,035–3,531 mg | 5 | 4,334–8,874 mg | 6–13 |
| 900 mg | 3,122–3,632 mg | 5 | 4,458–9,128 mg | 7–13 |
| 925 mg | 3,208–3,733 mg | 5–6 | 4,581–9,381 mg | 7–13 |
| 950 mg | 3,295–3,834 mg | 5–6 | 4,705–9,635 mg | 7–14 |
| 975 mg | 3,382–3,935 mg | 5–6 | 4,829–9,888 mg | 7–14 |
| 1,000 mg | 3,469–4,036 mg | 5–6 | 4,953–10,142 mg | 7–14 |
Source · Chemical formulas and NIH DSLD labels · snapshot 2026-08-10 · release 2026-08-10-f441aa9f · CSV · method