Three things to remember
- Read the amount and its serving basis together; two capsules are not one capsule.
- A component can already be included in a parent total. Do not add it twice.
- An undisclosed amount remains unknown; a calculation cannot fill an evidence gap.
Start with the line above the numbers
Before comparing ingredients, record the exact product, flavour, pack and market. Find the panel heading and serving size. US Supplement Facts rules describe a serving basis; a serving is not necessarily one capsule, one scoop or your personal daily requirement. For Indian and other-market packs, read the stated basis on that exact panel rather than assuming the US format applies.
Fictional example: a bottle has 60 capsules and declares 200 mg of a nutrient per two-capsule serving. That means 30 labelled servings, 100 mg per capsule and 6,000 mg declared nutrient across the bottle. It does not mean 200 mg in every capsule. Keep these three columns separate in a comparison: amount per labelled serving, number of units in that serving, and amount per unit.
Sources: US FDA · Supplement Facts, serving basis and proprietary blends ↗
Distinguish the mineral from its compound
NIH ODS explains that a US magnesium Supplement Facts amount refers to elemental magnesium, not the entire magnesium-containing compound. The form named in brackets describes its source. This is why the front label and nutrient panel can contain different numbers without necessarily contradicting each other.
Fictional example: the panel states “Magnesium 120 mg” and names magnesium citrate as the source. If another line identifies 800 mg of the citrate ingredient, do not add 120 and 800 to report 920 mg of magnesium. Record 120 mg as the declared elemental amount and retain the source form separately. If only the compound weight is available, mark elemental magnesium as unverified. Do not guess it from a generic internet percentage: mixtures, hydration and specifications can differ.
Sources: NIH ODS · Magnesium: elemental amount on Supplement Facts ↗
Read totals and their components as a hierarchy
Fish oil is not synonymous with EPA plus DHA. NIH ODS describes products containing a larger fish-oil amount with smaller EPA and DHA amounts inside it. Use the exact label, because the proportions vary. Similarly, powder weight and declared protein weight answer different questions.
Fictional oil panel: fish oil 1,000 mg, including EPA 180 mg and DHA 120 mg, per softgel. EPA plus DHA is 300 mg; it is included within the 1,000 mg oil amount. Adding all three lines produces an incorrect total of 1,300 mg. If the question is cost per gram of EPA plus DHA, use the disclosed 300 mg, not 1,000 mg. This arithmetic does not make different oils clinically interchangeable.
In your notes, indent the child amounts beneath the parent. When a database exports every row into a flat list, preserve this relationship. A searchable list of numbers is useful only if you still know which ones overlap.
Use percentages carefully; leave hidden amounts hidden
Fictional extract example: 500 mg of a named extract is explicitly standardised to 5% of a stated constituent. Multiplying 500 by 0.05 gives 25 mg of that constituent within the extract. It is not 525 mg of total active material. This conditional calculation is only as sound as the label statement; it does not establish absorption, batch measurement or a clinical benefit.
A percentage without a clear basis is not enough. Establish whether it applies to the full blend, a specific extract or another ingredient. If a number is qualified as “at least”, preserve that qualifier instead of presenting an exact tested amount.
US proprietary-blend labelling can give a combined weight without disclosing each component’s amount. The ingredient order is not a formula you can reverse-engineer. A 600 mg blend containing three ingredients does not establish 200 mg of each. Mark their individual amounts as undisclosed and avoid ranking those ingredients by an invented dose.
Sources: US FDA · Supplement Facts, serving basis and proprietary blends ↗
Keep the unit attached to every figure
One gram equals 1,000 mg; 1 mg equals 1,000 micrograms, written mcg or μg. Thus 250 mcg equals 0.25 mg, not 250 mg. NHS notes that converting International Units depends on the vitamin. Do not apply one IU conversion to every nutrient or chemical form.
Finish by writing a plain-language comparison sentence: “This exact label declares X mg of the named nutrient per Y capsules; this is the manufacturer’s statement.” Attach the source and date. If you cannot complete that sentence without guessing, pause the comparison at the missing field. More printed milligrams do not by themselves mean a better or more suitable purchase.
Sources: NHS · Milligrams, micrograms and International Units ↗
Common questions
Can a correct calculation verify the amount in my bottle?
No. It checks arithmetic using declared inputs. Verification of the contents of a particular batch is a separate evidence question.
Does the comparison quantity tell me how much to take?
No. It is a unit for comparing labels, not an intake recommendation.
Take the knowledge with you.
Compare the same form, active amount and intended use before comparing price. India and International listings have separate filters; some categories may have no listings in one market. Listings do not establish local stock or a need for a supplement. Shopping disclosures appear on product pages.
Sources & scope
This is a brand-independent editorial summary of the sources below, not an independent clinical review. Published reference values apply to their stated populations. Ingredient research does not verify a particular brand, batch or seller. No individual diagnosis, deficiency test or medical assessment is performed here.