Cow’s milk delivers about 8 grams of protein per cup, making it the highest-protein option among standard milks you’ll find in most grocery stores. But if you’re willing to look beyond the basics, ultra-filtered dairy milk pushes that number to 13 grams per cup, and sheep’s milk is the richest of all animal milks by protein density.
Standard Cow’s Milk Sets the Baseline
A cup of regular cow’s milk, whether whole, 2%, or skim, contains roughly 8 grams of protein. That protein is a mix of two types: about 80% casein, which digests slowly, and 20% whey, which digests quickly. This combination is one reason dairy milk scores so well on protein quality scales. On the PDCAAS, the standard measure of how well your body can use a protein source, cow’s milk scores a perfect 1.0 out of 1.0.
Fat content doesn’t meaningfully change the protein count. Whole milk, reduced fat, and skim all land in the same 8-gram range per cup. What changes is the calorie count, from around 150 calories for whole milk down to about 90 for skim.
Ultra-Filtered Milk Leads the Dairy Category
If you want the most protein from a cup of milk, ultra-filtered dairy milk is the clear winner at the store. Brands like Fairlife run regular cow’s milk through a fine filtration process that concentrates the protein while removing most of the lactose and sugar. The result: 13 grams of protein per cup, roughly 50% more than standard milk, with only 6 grams of sugar compared to regular milk’s 12 grams. It also delivers 380 mg of calcium per serving versus 276 mg in regular milk.
Because it’s still real dairy, ultra-filtered milk retains the same high protein quality score as standard cow’s milk. For people who are lactose intolerant, these products are also essentially lactose-free.
Sheep and Goat Milk Compared to Cow’s
Among animal milks, sheep’s milk has the highest protein concentration. Research comparing milk powders found sheep milk contained about 30 grams of protein per 100 grams of powder, compared to roughly 25 grams for both cow and goat milk. That translates to noticeably more protein per cup of liquid sheep’s milk as well, typically around 15 grams depending on the brand.
Goat milk lands very close to cow’s milk in protein content, with a similar amino acid profile and digestibility. It’s not a significant upgrade if protein is your main concern, though some people find it easier to digest due to differences in fat globule size.
How Plant Milks Stack Up
Plant-based milks vary dramatically in protein, from nearly zero to matching dairy. Here’s how the most common options compare per cup:
- Soy milk: 7 to 8 grams. The only mainstream plant milk that comes close to dairy. Soy is also a complete protein, meaning it contains all nine essential amino acids your body can’t make on its own.
- Pea protein milk: 8 grams. Brands like Ripple use pea protein isolate to match cow’s milk gram for gram, with 440 mg of calcium per cup (more than dairy). However, pea protein has a lower digestibility score of around 0.62 compared to dairy’s 1.0, so your body absorbs less of that protein in practice.
- Oat milk: 2 to 3 grams. Popular for its creamy texture in coffee, but not a meaningful protein source.
- Almond milk: 1 gram. Almond milk is mostly water with a small amount of ground almonds. It has 75% fewer calories than dairy milk, but the tradeoff is almost no protein.
The protein quality gap matters more than many labels suggest. Cow’s milk scores between 100 and 120 on the DIAAS, the newer and more precise protein quality measure. Pea protein scores around 62, and rice protein around 47. So even when a plant milk matches dairy on grams per cup, your body may extract significantly fewer usable amino acids from it.
Concentrated Dairy Products Go Even Higher
If you’re cooking or blending smoothies and want to pack in more protein, evaporated milk is worth knowing about. A cup of evaporated nonfat milk contains over 19 grams of protein, more than double what you get from regular milk. That’s because evaporated milk has had about 60% of its water removed, concentrating everything, including protein, calories, and sugar.
You wouldn’t drink evaporated milk straight (it’s thick and intensely flavored), but it’s useful in oatmeal, soups, or protein shakes where the consistency works in your favor.
Choosing the Right Milk for Your Goals
Your best pick depends on what you’re optimizing for. If protein per cup is all that matters and you’re fine with dairy, ultra-filtered milk at 13 grams is the most efficient choice on a standard grocery shelf. Sheep’s milk edges even higher but is harder to find and more expensive.
If you avoid dairy, soy milk is the strongest plant-based option, both in total grams and in how well your body absorbs it. Pea protein milks match the number on the label but deliver less usable protein due to lower digestibility. Oat and almond milk are fine for other purposes, but they’re not protein sources in any practical sense. One cup of almond milk gives you the same protein as a single bite of chicken breast.
For context, most adults need somewhere between 50 and 70 grams of protein daily. A cup of ultra-filtered milk covers roughly 20 to 25% of that target. A cup of almond milk covers about 1.5%.