What is the difference between omega-3 and fish oil?

Omega-3 is a family of fatty acids. Fish oil is an oil obtained from fish that can contain omega-3 fatty acids. The terms describe different things: the type of fatty acid and the oil’s source.^[1][2]

That is why “1,000 mg fish oil” on a pack does not automatically mean “1,000 mg omega-3”. An omega-3 supplement does not have to contain fish oil either.

What does omega-3 mean?

Omega-3 includes several fatty acids, among them DHA, EPA and ALA. These are separate substances within the same family.^[1][2]

A label may list those names individually alongside a declaration such as “total omega-3”. That total can differ from DHA+EPA because it can include other omega-3 fatty acids.

DHA+EPA means only the combined amount of DHA and EPA. It is not another name for all the omega-3 in a product.

What is fish oil?

Fish oil is oil obtained from fish. In supplements, it can contain DHA and EPA alongside other components. The declared amount of oil and the declared amount of DHA+EPA are therefore different figures.^[1]

Two fish oil products can also have different compositions. Their DHA and EPA amounts and relative proportions can vary.^[1][3] The words “fish oil” alone do not establish those figures.

You cannot use a fixed percentage to convert the oil amount into DHA+EPA. You need information for the specific pack.

Why can the same label declare 1,000 mg fish oil and 300 mg DHA+EPA?

Because DHA and EPA are part of the oil. Do not add them on top of the oil’s weight.

This fictional example refers to one capsule. The figures are invented to explain the terms; they are not test results.

The 120 mg DHA and 180 mg EPA add up to 300 mg DHA+EPA. That 300 mg is included in the 360 mg total omega-3, which is included in the 1,000 mg fish oil.

In this calculation example, the omega-3 total includes another 60 mg without a further breakdown. The table does not identify which other omega-3 fatty acids these are.

The oil’s remaining contents are not described here either. The difference from the oil amount is not a measure of “filler” or impurities.

These figures are not separate quantities to add together. Doing so would count the same contents more than once.

Does omega-3 always come from fish?

No. Algal oil can contain DHA and, depending on the product, EPA too. Flaxseed oil is one source of ALA.^[1][2]

The term “omega-3” therefore does not establish whether the oil comes from fish, algae or another source. Check the ingredients list and the declared oil source.

Read more about oil sources in Fish oil or algal oil: what is the difference?. For the distinction between fatty acids, see How does ALA differ from DHA and EPA?.

The form in which the product is sold is another separate detail. “Capsules”, for example, does not identify the oil source. Check the other ingredients too if you want to establish the full composition.

Which figures should you use to compare products?

Start with the DHA+EPA amount expressed on the same basis. Check whether figures refer to one capsule, two capsules or a millilitre.

Next, check how many capsules or millilitres the pack contains. You can then calculate the total declared DHA+EPA in the pack. Convert that total into grams: 1,000 mg is 1 gram. Divide the pack price by that number of grams.

A price per gram of fish oil and a price per gram of DHA+EPA use different quantities as their basis. Do not treat them as the same price figure.

If only the oil amount is known, it does not establish an exact DHA+EPA total. A missing declaration remains unknown; do not fill the gap using a similar product’s composition.

For the full reading and calculation sequence, see How to read an omega-3 supplement label.

What do these terms say about quality?

“Fish oil” describes the oil source. “Omega-3” describes a family of fatty acids. Neither declaration establishes what has been measured in a product or batch.

Statements about oxidation, contaminants or measured DHA+EPA content require relevant measurement evidence. That includes the source, date and material examined, with a batch connection where applicable. A label declaration is not itself a laboratory result.

On SUPPFAX, DHA+EPA amounts declared on labels form the basis of the price comparison. This puts costs on a common measure of contents. The calculation does not turn a label declaration into a test result or produce a quality score.

Sources

Consulted on 31 October 2026.

1. NIH Office of Dietary Supplements — Omega-3 Fatty Acids, Health Professional Fact Sheet. For the omega-3 family and the differences between oil amounts, fatty acid amounts and supplement formulations. Stated source update: 22 August 2025. ↩ ↩ ↩ ↩ ↩
2. Voedingscentrum — Omega 3 en omega 6 (Dutch). For Dutch terminology and examples of omega-3 sources. ↩ ↩ ↩
3. GOED Voluntary Monograph, version 8.1, 6 January 2022 (PDF). For different DHA and EPA proportions and expressing their amounts separately and as a combined total. ↩