The Best Protein Sources by Cost, Calorie, and DIAAS Score
Chicken is the obvious answer, but it is not always the best. Here is the actual ranking when you include cost per gram and digestibility.
Most "best protein source" articles rank by grams per serving and stop there. Useful, but incomplete. Three things actually matter: how many grams of protein per dollar, how many calories come along for the ride, and how much your body actually absorbs (the DIAAS score). When you weight all three, the rankings shift in surprising ways.
The DIAAS quick primer
DIAAS (Digestible Indispensable Amino Acid Score) is the modern replacement for the old PDCAAS rating. A score of 1.0 means complete and fully digestible. Whey isolate scores 1.09, beef scores 1.11, soy isolate 0.92, pea isolate 0.79, and most grains land around 0.4-0.6. This is why mixing rice with legumes works — the amino acid gaps fill each other.
Cheapest protein per gram (US, 2026)
- Whole eggs — about 6 cents per gram of protein, DIAAS 1.16. Hard to beat unless you live somewhere eggs cost more than meat.
- Whey protein concentrate — 5-7 cents per gram, DIAAS 1.0+. Cheapest powdered option.
- Canned tuna — 8-10 cents per gram, DIAAS 1.0+. Long shelf life.
- Greek yogurt (store brand) — 9-11 cents per gram, DIAAS 1.05.
- Chicken thighs (bone-in) — 10-13 cents per gram, DIAAS 1.08. Cheaper than breast and harder to overcook.
Lowest calories per gram of protein
- Egg whites — 4 calories per gram of protein
- Whey isolate — 4-4.5 cal/g
- Chicken breast — 4.5 cal/g
- Cod / white fish — 4.5 cal/g
- Plain non-fat Greek yogurt — 4.8 cal/g
Compare to whole milk (15 cal/g of protein) or peanut butter (about 24 cal/g). The cleaner the source, the lower the price per gram of protein in calories.
Best plant sources for muscle building
If you eat plant-based, prioritize complete proteins or smart blends:
- Soy isolate / tempeh — DIAAS 0.92, the only plant source close to whey.
- Pea isolate — DIAAS 0.79 alone, but combined with rice protein hits 1.0+.
- Quinoa — DIAAS 0.83, one of the few complete plant grains.
- Mycoprotein (Quorn) — DIAAS 0.91, performs near-identically to whey for muscle synthesis in studies.
The "looks good but isn't" list
Some popular sources score worse than their reputation:
- Almonds — 21 g protein per 100 g looks great, but DIAAS is 0.40 and 100 g is also 575 calories.
- Peanut butter — 25 g protein per 100 g, but DIAAS 0.51 and 600 calories.
- Bacon — 12 g protein per 100 g, but mostly fat. Use as flavor, not a protein anchor.
- Beef jerky — high protein, but expensive per gram and high in sodium.
The practical lineup
For 80% of people who train and want to hit 1.6-2.2 g/kg cheaply: chicken thighs or breast as the dinner anchor, eggs for breakfast, Greek yogurt or canned tuna for snacks, and one whey shake for the gap. That mix lands around 8-12 cents per gram of protein, hits DIAAS 1.0+, and stays under 5 calories per gram of protein.
Plug your daily target into the protein calculator and use the food source breakdown to plan a real menu — not just numbers in a spreadsheet.