Same elemental magnesium · two salts · snapshot 2026-08-10
Magnesium aspartate vs carbonate: 1,279–2,670 vs 694–807 mg of compound for 200 mg of magnesium
Magnesium aspartate is 7.5–15.6% elemental magnesium and magnesium carbonate is 24.8–28.8%, so 200 mg of magnesium needs 1,279–2,670 mg of aspartate against 694–807 mg of carbonate: 2–4 vs 1–2 size 00 capsules at powder density 0.8 g/mL, the top of the usual 0.6–0.8 range. 0 of 15 capsule labels naming aspartate alone are above the assumed size 000 capacity at powder density 0.8 g/mL, against none for carbonate (no capsule label names it alone). 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 · aspartate 639–1,335 |
| 200 mg magnesium |
| carbonate 694–807 · aspartate 1,279–2,670 |
| 400 mg magnesium |
| carbonate 1,387–1,614 · aspartate 2,558–5,340 |
Data release 2026-08-10-f441aa9f · registry snapshot 2026-08-10 · latest price observation 2026-11-02 · chemistry 2026-10-17
How much aspartate or carbonate carries the same elemental magnesium?
At the same elemental amount, carbonate (24.8–28.8% magnesium) always needs less compound than aspartate (7.5–15.6%): for 400 mg of magnesium, 1,387–1,614 mg against 2,558–5,340 mg. That is the mass of powder per dose; how much of it is absorbed is what the studies below measured.
computed| Elemental magnesium | aspartate compound | aspartate size 00 | carbonate compound | carbonate size 00 |
|---|---|---|---|---|
| 100 mg | 639–1,335 mg | 1–2 | 347–404 mg | 1 |
| 200 mg | 1,279–2,670 mg | 2–4 | 694–807 mg | 1–2 |
| 400 mg | 2,558–5,340 mg | 4–8 | 1,387–1,614 mg | 2–3 |
aspartate: 1:1 magnesium aspartate 15.64%; bis(hydrogen aspartate) 8.42%, its dihydrate 7.49%; stoichiometry and hydration unresolved; carbonate: anhydrous or hydrated; labels rarely state which; 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
0 of 15 capsule labels naming aspartate alone are above the assumed size 000 capacity at powder density 0.8 g/mL, against none for carbonate (no capsule label names it alone). 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 |
|---|---|---|---|---|
| aspartate | 15 | 13 | 2 | 0 |
| carbonate | 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 |
|---|---|---|---|---|
| aspartate | 0 | none | none | 2026-11-02 |
| carbonate | 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 aspartate and carbonate side by side?
One study in the PubMed-checked registry measured both salts in the same design; 2 involve aspartate and 2 involve carbonate 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 |
| 2001 | Bioavailability of US commercial magnesium preparations | oxide, chloride, lactate, aspartate | 11794633 |
| 2022 | Effects of short-term magnesium supplementation on ionized, total magnesium and other relevant electrolytes levels. | oxide, citrate, carbonate | 35041150 |
Source · PubMed-checked study registry · registry checked 2026-08-10 · release 2026-08-10-f441aa9f · CSV · method
How many labels name both aspartate and carbonate?
No label names both aspartate and carbonate as of 2026-08-10, against 46 labels naming aspartate and 23 naming carbonate.
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 | aspartate compound | aspartate size 00 | carbonate compound | carbonate size 00 |
|---|---|---|---|---|
| 25 mg | 160–334 mg | 1 | 87–101 mg | 1 |
| 50 mg | 320–668 mg | 1 | 173–202 mg | 1 |
| 75 mg | 480–1,001 mg | 1–2 | 260–303 mg | 1 |
| 100 mg | 639–1,335 mg | 1–2 | 347–404 mg | 1 |
| 125 mg | 799–1,669 mg | 2–3 | 434–504 mg | 1 |
| 150 mg | 959–2,003 mg | 2–3 | 520–605 mg | 1 |
| 175 mg | 1,119–2,336 mg | 2–4 | 607–706 mg | 1 |
| 200 mg | 1,279–2,670 mg | 2–4 | 694–807 mg | 1–2 |
32 additional rows
| Elemental magnesium | aspartate compound | aspartate size 00 | carbonate compound | carbonate size 00 |
|---|---|---|---|---|
| 225 mg | 1,439–3,004 mg | 2–5 | 780–908 mg | 2 |
| 250 mg | 1,598–3,338 mg | 3–5 | 867–1,009 mg | 2 |
| 275 mg | 1,758–3,672 mg | 3–6 | 954–1,110 mg | 2 |
| 300 mg | 1,918–4,005 mg | 3–6 | 1,041–1,211 mg | 2 |
| 325 mg | 2,078–4,339 mg | 3–6 | 1,127–1,312 mg | 2 |
| 350 mg | 2,238–4,673 mg | 4–7 | 1,214–1,412 mg | 2 |
| 375 mg | 2,398–5,007 mg | 4–7 | 1,301–1,513 mg | 2–3 |
| 400 mg | 2,558–5,340 mg | 4–8 | 1,387–1,614 mg | 2–3 |
| 425 mg | 2,717–5,674 mg | 4–8 | 1,474–1,715 mg | 3 |
| 450 mg | 2,877–6,008 mg | 4–9 | 1,561–1,816 mg | 3 |
| 475 mg | 3,037–6,342 mg | 5–9 | 1,648–1,917 mg | 3 |
| 500 mg | 3,197–6,676 mg | 5–10 | 1,734–2,018 mg | 3 |
| 525 mg | 3,357–7,009 mg | 5–10 | 1,821–2,119 mg | 3 |
| 550 mg | 3,517–7,343 mg | 5–11 | 1,908–2,220 mg | 3–4 |
| 575 mg | 3,676–7,677 mg | 6–11 | 1,994–2,320 mg | 3–4 |
| 600 mg | 3,836–8,011 mg | 6–11 | 2,081–2,421 mg | 3–4 |
| 625 mg | 3,996–8,344 mg | 6–12 | 2,168–2,522 mg | 3–4 |
| 650 mg | 4,156–8,678 mg | 6–12 | 2,255–2,623 mg | 4 |
| 675 mg | 4,316–9,012 mg | 6–13 | 2,341–2,724 mg | 4 |
| 700 mg | 4,476–9,346 mg | 7–13 | 2,428–2,825 mg | 4 |
| 725 mg | 4,636–9,680 mg | 7–14 | 2,515–2,926 mg | 4–5 |
| 750 mg | 4,795–10,013 mg | 7–14 | 2,601–3,027 mg | 4–5 |
| 775 mg | 4,955–10,347 mg | 7–15 | 2,688–3,128 mg | 4–5 |
| 800 mg | 5,115–10,681 mg | 8–15 | 2,775–3,228 mg | 4–5 |
| 825 mg | 5,275–11,015 mg | 8–16 | 2,862–3,329 mg | 4–5 |
| 850 mg | 5,435–11,348 mg | 8–16 | 2,948–3,430 mg | 5 |
| 875 mg | 5,595–11,682 mg | 8–17 | 3,035–3,531 mg | 5 |
| 900 mg | 5,754–12,016 mg | 8–17 | 3,122–3,632 mg | 5 |
| 925 mg | 5,914–12,350 mg | 9–17 | 3,208–3,733 mg | 5–6 |
| 950 mg | 6,074–12,684 mg | 9–18 | 3,295–3,834 mg | 5–6 |
| 975 mg | 6,234–13,017 mg | 9–18 | 3,382–3,935 mg | 5–6 |
| 1,000 mg | 6,394–13,351 mg | 9–19 | 3,469–4,036 mg | 5–6 |
Source · Chemical formulas and NIH DSLD labels · snapshot 2026-08-10 · release 2026-08-10-f441aa9f · CSV · method