Formula
This page discloses every calculation behind the metrics. Anyone who wants to redo the arithmetic will find all formulas and reference figures here. All statements are descriptive: content, amount, price and dosage form. Statements about effect or benefit are not part of this comparison.
Quality before price
Default sorting prioritises documented batch measurements, then linked laboratory reports, then fully sourced active declarations with identified forms. Incomplete evidence follows. Reports with measurements outside a stated criterion are ranked last. Comparable price breaks ties within the same evidence level.
This ranks documentation, not effectiveness, purity or health benefit. A manufacturer report is not an independent test. A study of an ingredient does not validate the specific product. Missing evidence means unknown, not bad; an older batch report does not prove the quality of your pack.
Community votes are unverified experiences and do not affect this ordering. Vegan means an explicit linked product declaration, not our own certification. Price comparisons cover observed shops only; codes show their check date and conditions. Deal comparisons require at least five observed days within the previous 30 days, excluding today and without using recommended retail prices as the discount baseline.
A compound consists only partly of the nutrient itself. At a mass share of 0.162, 500 mg of magnesium citrate contain about 81 mg of elemental magnesium; at 0.603, 500 mg of magnesium oxide contain about 302 mg. The same number on the label therefore means a fourfold difference in content.
Where the label already states the elemental content ("of which magnesium: 300 mg"), no second conversion is applied. The mass shares come from a hand-maintained compound table; every entry carries a source. When a factor is corrected, all affected products change at once, because the elemental content is never stored — it is always calculated.
We compare the product price after an eligible unconditional public code, excluding shipping. The cheapest fresh in-stock offer supplies all price metrics. Out-of-stock or expired observations remain visible but do not feed rankings or alerts. Delivery charges and free-shipping thresholds are shown separately only with a source, destination, conditions and checked date. Unknown delivery never blocks product-price comparisons.
The serving is the unit the label defines — one scoop, two capsules, five drops. It is what makes powders and capsules line up next to each other in the first place.
Price per serving still depends on how large the manufacturer defines a serving. Only the price per gram of elemental active makes dosing neutral: a powder with 400 mg of elemental magnesium per serving and a capsule with 100 mg land on the same scale.
For omega-3 the reference figure is EPA plus DHA, not a single fatty acid and not the amount of oil. For vitamin D3 it is cholecalciferol.
Price per day factors in the manufacturer's stated servings per day. It comes last on purpose: those statements are manufacturer figures and vary between otherwise comparable products.
A kilogram of powder is a statement about fill weight, not about active content. Magnesium citrate is roughly 16 % magnesium, magnesium oxide roughly 60 %. On price per kilogram the winner is the product with the cheapest carrier material — flavourings, sweeteners and anti-caking agents included. Price per kilogram therefore rewards the exact opposite of what is meant to be compared.
A capsule is not a unit of measurement. Two packages of 120 capsules each can hold 100 mg and 400 mg of elemental active per capsule, and the stated serving can be one capsule or four. Price per 100 units compares shells, not contents.
Both figures are easy to derive from a price-comparison feed — which is exactly why they are common. But they assume that packages contain the same thing. Supplements do not.
The NRV share is a labelling figure from the Food Information Regulation (EU) No 1169/2011, Annex XIII. It is given here purely descriptively, so that the order of magnitude of a serving can be placed. It is not a recommendation, not a statement about requirement and not a statement about effect.
If a figure is missing — servings per package, the active declaration, the servings per day or an in-stock offer — the affected metric is not calculated and not estimated. It appears as a missing value, and the variant stays in the list anyway, because a missing figure is itself information about the product. Sorting places such variants at the end instead of hiding them.
Calculations run unrounded; rounding happens only at display time. Monetary values are held internally in cents. Active amounts are shown in micrograms, milligrams or grams — whichever unit shows the magnitude without leading zeros. Converted, never altered.
Every offer carries the date it was recorded. The price may have changed between that recording and your visit; the price in the shop at the time of purchase is always the one that counts. Links to shops are ordinary links without tracking. The order in lists and comparisons follows the metrics. A code that applies to everyone without conditions is included in the price metrics — base price, discount and final price are always shown side by side. A code with a condition, such as a minimum order value or a restriction to first-time customers, is shown but explicitly not included: its value depends on your basket, not on the product. Expired codes are removed and no longer shown.
Data sources and limits
Every fraction is calculated from the chemical formula rather than typed in. The “500 mg →” column shows how much of the nutrient 500 mg of the substance delivers.
| Compound | Share of pure active | 500 mg → | Source |
|---|---|---|---|
| Magnesium oxide | 60.3% | 302 mg | MgO, M = 40.304 g/mol |
| Magnesium hydroxide | 41.7% | 208 mg | Mg(OH)2, M = 58.319 g/mol |
| Magnesium carbonate | 28.8% | 144 mg | MgCO3, M = 84.313 g/mol |
| Magnesium chloride | 25.5% | 128 mg | MgCl2, M = 95.205 g/mol |
| Magnesium sulfate | 20.2% | 101 mg | MgSO4, M = 120.361 g/mol |
| Magnesium citrate | 16.2% | 80.8 mg | Mg3(C6H5O7)2, M = 451.113 g/mol. Trimagnesium dicitrate — three magnesium atoms per formula unit. |
| Magnesium malate | 15.5% | 77.7 mg | MgC4H4O5, M = 156.376 g/mol |
| Magnesium bisglycinate | 14.1% | 70.5 mg | Mg(C2H4NO2)2, M = 172.423 g/mol |
| Magnesium glycerophosphate | 12.5% | 62.5 mg | MgC3H7O6P, M = 194.362 g/mol |
| Magnesium lactate | 12% | 60 mg | Mg(C3H5O3)2, M = 202.445 g/mol |
| Magnesium taurate | 8.9% | 44.6 mg | Mg(C2H6NO3S)2, M = 272.573 g/mol |
| Magnesium aspartate | 8.4% | 42.1 mg | Mg(C4H6NO4)2, M = 288.495 g/mol |
| Magnesium L-threonate | 8.3% | 41.3 mg | Mg(C4H7O5)2, M = 294.495 g/mol |
| Magnesium orotate | 7.3% | 36.3 mg | Mg(C5H3N2O4)2, M = 334.483 g/mol |
| Compound | Share of pure active | 500 mg → | Source |
|---|---|---|---|
| Zinc oxide | 80.3% | 402 mg | ZnO, M = 81.379 g/mol |
| Zinc sulfate | 40.5% | 202 mg | ZnSO4, M = 161.436 g/mol |
| Zinc acetate | 35.6% | 178 mg | Zn(C2H3O2)2, M = 183.468 g/mol |
| Zinc citrate | 34.2% | 171 mg | Zn3(C6H5O7)2, M = 574.338 g/mol. Trizinc dicitrate — three zinc atoms per formula unit. |
| Zinc bisglycinate | 30.6% | 153 mg | Zn(C2H4NO2)2, M = 213.498 g/mol |
| Zinc lactate | 26.8% | 134 mg | Zn(C3H5O3)2, M = 243.520 g/mol |
| Zinc picolinate | 21.1% | 106 mg | Zn(C6H4NO2)2, M = 309.586 g/mol |
| Zinc aspartate | 19.8% | 99.2 mg | Zn(C4H6NO4)2, M = 329.570 g/mol |
| Zinc orotate | 17.4% | 87 mg | Zn(C5H3N2O4)2, M = 375.558 g/mol |
| Zinc gluconate | 14.3% | 71.7 mg | Zn(C6H11O7)2, M = 455.674 g/mol |
These forms are declared directly as active amount on the label — converting via molar mass would be wrong. On file: Cholecalciferol.
These forms are declared directly as active amount on the label — converting via molar mass would be wrong. On file: Menaquinone-7 (MK-7), Menaquinone-4 (MK-4).
Different forms are not comparable mass for mass, so they are kept separate.
| Compound | Share of pure active | 500 mg → | Source |
|---|---|---|---|
| EPA (declared directly) | 100% | 500 mg | C20H30O2, M = 302.458 g/mol. Labels state EPA in mg per serving — converting would be wrong. |
| EPA triglyceride | 96% | 480 mg | C63H92O6, M = 945.423 g/mol. Tri-EPA glycerol as the calculation model — three EPA residues on glycerol. |
| EPA ethyl ester | 91.5% | 458 mg | C22H34O2, M = 330.512 g/mol. Reference is the free acid EPA. |
| Compound | Share of pure active | 500 mg → | Source |
|---|---|---|---|
| DHA (declared directly) | 100% | 500 mg | C22H32O2, M = 328.496 g/mol. Labels state DHA in mg per serving — converting would be wrong. |
| DHA triglyceride | 96.3% | 481 mg | C69H98O6, M = 1023.537 g/mol. Tri-DHA glycerol as the calculation model — three DHA residues on glycerol. |
| DHA ethyl ester | 92.1% | 461 mg | C24H36O2, M = 356.550 g/mol. Reference is the free acid DHA. |
| Compound | Share of pure active | 500 mg → | Source |
|---|---|---|---|
| Creatine anhydrous | 100% | 500 mg | C4H9N3O2, M = 131.135 g/mol. Anhydrous form — the substance is the active ingredient. |
| Creatine monohydrate | 87.9% | 440 mg | C4H9N3O2 · H2O, M = 149.150 g/mol |
| Creatine HCl | 78.2% | 391 mg | C4H9N3O2 · HCl, M = 167.593 g/mol |
| Creatine malate | 74.6% | 373 mg | 3 C4H9N3O2 · C4H6O5, M = 527.492 g/mol. Tri-creatine malate — three creatine molecules per malic acid. |
| Creatine citrate | 67.2% | 336 mg | 3 C4H9N3O2 · C6H8O7, M = 585.528 g/mol. Tri-creatine citrate — three creatine molecules per citric acid. |
| Creatine ethyl ester HCl | 67% | 335 mg | C6H13N3O2 · HCl, M = 195.647 g/mol. Reference is the creatine equivalent after the ethyl group is cleaved off. |
Prices and availability come from partner shops' product feeds and are refreshed daily. Nutrient values come from the manufacturer's label and are not lab-verified. Elemental shares are calculated from molar masses; every compound carries its source. Where a value is missing we show the gap instead of an estimate.