Fish-oil packaging often gives the oil weight the largest type. That number describes the oil mixture, not necessarily the amount of the long-chain omega-3 fatty acids EPA and DHA. For a useful product comparison, those quantities must remain separate.

Three numbers with different meanings

• Total oil is the weight of fish oil or another source oil in the serving.
• EPA is the declared amount of eicosapentaenoic acid.
• DHA is the declared amount of docosahexaenoic acid.

Other fatty acids can make up the remainder of the oil. Therefore, total oil cannot be substituted for EPA plus DHA.

Why the difference can be large

The NIH Office of Dietary Supplements gives a typical example of a 1,000 mg fish-oil supplement containing about 180 mg EPA and 120 mg DHA, while emphasizing that doses vary widely. In that illustrative product, EPA plus DHA totals 300 mg—not 1,000 mg. Concentrated products can have a different relationship, which is why the actual label must be read.

Read the panel in this order

1. Note the serving size: one softgel, two softgels, or another amount.
2. Find the fish oil or source-oil amount, if declared.
3. Find EPA and DHA as separate rows or clearly itemized subcomponents.
4. Add EPA and DHA only when both values refer to the same serving.
5. Divide by serving units only if you want a per-softgel figure.

If a label says “omega-3 fatty acids” without breaking out EPA and DHA, LabelLens does not invent the split. If it declares EPA and DHA but not total oil, the active comparison can still be made while total oil remains unavailable.

Concentration is informative, not a quality verdict

One descriptive calculation is the EPA-plus-DHA share of the declared oil: (EPA + DHA) ÷ total oil × 100. This can show how concentrated the declared actives are, but it does not prove purity, oxidation status, freshness, absorption, or clinical effectiveness. Those require different evidence.

Cost comparisons need the same denominator

Cost per bottle favors larger bottles even when serving sizes differ. Cost per label serving is better for routine comparison. Cost per 1,000 mg of declared EPA plus DHA can answer a narrower concentration-value question, but only when the source fields are complete and refer to the same offer and serving basis.

Common mistakes

• Comparing the front-label fish-oil weight with another product’s EPA-plus-DHA total.
• Reading a two-softgel amount as if it were per softgel.
• Assuming “omega-3” means only EPA and DHA.
• Treating concentration as a complete safety or quality assessment.
• Using a retailer title when the current Supplement Facts panel says something different.

LabelLens preserves each layer because a transparent “not declared” is more useful than a confident but unsupported conversion.

Sources and further reading

• NIH Office of Dietary Supplements: Omega-3 Fatty Acids — Health Professional Fact Sheet
• FDA: Dietary Supplement Labeling Guide, nutrition labeling
• Electronic Code of Federal Regulations: 21 CFR 101.36

Source links were checked on July 18, 2026.