Short answer
Butter is defined in the US as a product made exclusively from milk or cream, while margarine is a formulated blend of edible fats or oils—often from non-dairy sources—plus water or milk, and must include added vitamin A. 1 2
Butter is a dairy product with a single-source fat, while margarine is a manufactured emulsion that may use various fat sources and additional ingredients.
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At a glance
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| Question | butter | margarine |
|---|---|---|
| Main fat source | Milk or cream | Vegetable, animal, or marine oils |
| Required additives | None required | Vitamin A, optional others |
What each thing is
Butter. Butter is a dairy product made from milk or cream, or both, with or without salt or coloring, and must contain at least 80% milk fat by weight under US law. 1
Margarine. Margarine is a standardized spread or liquid emulsion containing at least 80% fat from permitted edible oils or fats, with required vitamin A. Its other permitted ingredients can vary by formulation. 2
Key differences
The core distinction is the source and composition of the fat: butter must be made from milk or cream, while margarine uses a blend of edible fats or oils, which may be plant, animal, or marine derived. 1 2
How to tell them apart
In practice, butter is labeled as such and lists only dairy ingredients, while margarine labels show a mix of oils and required vitamin A. However, some spreads may resemble either product, so checking the ingredient list is necessary. 1 2
Where they overlap
Both butter and margarine must contain at least 80% fat by weight in the US, and both can be sold in stick or tub forms, sometimes with added salt or coloring for similar appearance. 1 2
Edge cases
Some margarine products include milk or milk proteins, and certain spreads may not meet the 80% fat threshold, so they are not legally butter or margarine under US standards. 2
Why the distinction exists
US regulations define butter strictly to preserve its traditional dairy identity, while margarine’s standard allows a wider range of fats and additives to create a butter-like product from non-dairy sources. 1 2
Common misconceptions
It is a common misconception that margarine is always dairy-free; US standards allow margarine to contain milk or milk products as part of its water phase ingredients. 2
Examples
A shopper comparing stick butter and margarine in a US grocery store will find butter labeled as made from cream, while margarine lists oils, water, and vitamin A among its ingredients, reflecting their regulatory definitions. 1 2
Sources
Sources checked October 3, 2026.
- US Congress — 21 USC 321a: Butter defined. Butter source and milkfat definition.
- US Food and Drug Administration — 21 CFR 166.110: Margarine. Margarine standardized composition.