Best protein powders, ranked by $/gram of leucine
We ranked 14 protein powders by the metric that actually matters, cost per gram of leucine delivered, with third-party testing filters.
Costco Kirkland Signature Whey Protein
Informed Sport certified, ~5.5 g leucine per 25 g serving [VERIFY current label], lands near $0.013/g protein at Costco warehouse pricing. Nothing with a published COA and a clean sweetener profile beats it on unit economics. If Costco access is blocked, Bulk Supplements Whey Isolate is the mail-order equivalent.
Every product, ranked.
| # | Notes | Confidence | |||
|---|---|---|---|---|---|
| 01 | Costco Kirkland Signature Whey Protein | Best overall ($/g leucine) | 01 | Informed Sport tested, ~25 g protein and ~5.5 g leucine per scoop [VERIFY current label], ~$0.013/g protein at warehouse pricing. Sucralose sweetened; no proprietary blend. The default recommendation for readers with Costco access. | High |
| 02 | Bulk Supplements Whey Protein Isolate | Best budget mail-order | 02 | Raw commodity WPI, COA published per lot on bulksupplements.com. Unflavored, unsweetened, ~23 g protein per 25 g scoop, ~5.2 g leucine. $0.014/g protein in 5 kg bags. For the reader who mixes powder into oats and doesn't care about shake-house flavor. | High |
| 03 | Transparent Labs ProteinSeries 100% Grass-Fed Whey Isolate | Best premium isolate | 03 | Informed Sport certified, 28 g protein per scoop, ~6.6 g leucine, stevia + monk fruit (no sucralose). Grass-fed source matters for a subset of readers. ~$0.032/g protein, 2.4x the Kirkland floor for a cleaner label and higher per-serve leucine. | High |
| 04 | Momentous Essential Grass-Fed Whey | Best NSF Certified for Sport | 04 | NSF Certified for Sport (the strictest tested tier), 20 g protein, ~5 g leucine per serving. Attia-adjacent brand, sold DTC. ~$0.058/g protein. Premium pricing earns a label guarantee that matters for athletes subject to anti-doping testing. | Medium |
| 05 | Legion Whey+ | Best transparent-label premium | 05 | Informed Choice tested, 22 g protein and ~5.5 g leucine per serving, stevia sweetened. Published lab reports on every batch. ~$0.038/g protein. Middle-of-the-premium-shelf with the best transparency documentation. | Medium |
| 06 | Optimum Nutrition Gold Standard 100% Whey | Category reference | 06 | Informed Choice tested (select SKUs), 24 g protein, ~5.5 g leucine per scoop. The category benchmark for 15+ years. ~$0.025/g protein. Not the cheapest, not the cleanest; included as the anchor every other product gets compared to. | Medium |
| 07 | Dymatize ISO100 | Best hydrolyzed isolate | 07 | Informed Choice tested, hydrolyzed whey isolate, 25 g protein and ~5.5 g leucine per serving. Hydrolysis speeds absorption but doesn't raise MPS ceiling in Reidy et al. 2013. ~$0.035/g protein. Buy only if rapid digestion matters (e.g., peri-workout in a fasted state). | Medium |
| 08 | MyProtein Impact Whey | Best UK/EU budget | 08 | Informed Sport certified on flagged SKUs, 21 g protein and ~4.5 g leucine per 25 g scoop. Low $/g in 5 kg bags, but leucine per serving is the lowest in this ranking. ~$0.017/g protein. Best for European readers without Costco access. | Medium |
| 09 | Ritual Essential Protein | Best pregnancy/postpartum formulated | 09 | Pea-based, traceable sources, 20 g protein per serving with ~1.6 g leucine, below the ~2.5-3 g leucine threshold Moore 2015 associates with maximal MPS. Add 2.5 g free leucine to hit threshold. ~$0.120/g protein. Pay for the sourcing, not the macros. | Medium |
| 10 | Klean Athlete Klean Isolate | Best clinical-grade | 10 | NSF Certified for Sport, WPI base, 20 g protein per scoop, ~5.2 g leucine. Unsweetened or lightly stevia-sweetened. ~$0.060/g protein. The pick when a physician or team nutritionist is involved. | Medium |
| 11 | Needed Collagen Protein Powder | Collagen reference (not primary protein) | 11 | Grass-fed collagen peptides, 20 g protein per serving but leucine is negligible and collagen doesn't trigger MPS (Oikawa 2020). Discussed only to flag: collagen is a joint/skin supplement, not a muscle-protein source. Not a substitute for whey. | Medium |
| 12 | Promix Whey Isolate | Grass-fed alternative | 12 | Grass-fed whey isolate, third-party tested (in-house + lot-level COA), 25 g protein and ~5.8 g leucine per serving. Unflavored option is genuinely unflavored. ~$0.044/g protein. A direct alternative to Transparent Labs if you prefer their label. | Medium |
Named, with the reason.
Orgain Organic Protein
Skip (weak leucine ratio)Pea/brown rice blend, 21 g protein per serving but only ~1.6 g leucine. Organic doesn't fix the amino profile. If vegan, stack with 2-3 g free leucine or move to a pea-soy blend with a published COA.
Muscle Milk / Quest / any proprietary blend
Skip (no ranking)Proprietary blends obscure the whey-to-casein-to-filler ratio. Muscle Milk has faced class-action amino-spiking litigation (2015, 2018). Without lot-level leucine disclosure we can't compute $/g leucine. We do not rank these.
How this was specified
- 01Inputs measured
- Retail price (dated) · label claim · Certificate of Analysis · third-party test (Informed Sport / NSF / ConsumerLab / Clean Label) · leucine per serving from COA, not marketing.
- 02Protocols tested
- Per-kg target from four literature ranges (IOM RDA, Phillips 2017, Morton 2018, ISSN). Brands scored against Moore 2015 leucine-per-dose threshold (~0.4 g/kg).
- 03Cost-basis verified
- $/gram of protein and $/gram of leucine at warehouse pricing (Costco), mail-order (Amazon), and DTC retail. Re-checked quarterly, flagged when drift exceeds 15%.
- 04Confidence level
- High on ranked order. Medium on absolute $/g (prices drift). Low on serving-size claims where COA is older than 18 months, flagged [VERIFY].
What people ask us most.
- Why $/gram of leucine and not $/gram of protein?
- Leucine is the limiting amino acid for muscle protein synthesis (Norton & Layman 2006). A serving that delivers 25 g protein but only 1.6 g leucine, common for collagen or pea isolate, won't maximally trigger MPS the way 20 g of whey with 2.5 g leucine will. $/g protein rewards bulk; $/g leucine rewards what the muscle actually uses. Both matter, which is why we show both.
- Is grass-fed whey worth the premium?
- For amino acid content, no. Multiple analyses show grass-fed vs conventional whey are indistinguishable on protein and leucine per gram. Grass-fed upgrades trace fatty acids (slightly higher CLA, omega-3) in whole dairy, but those are stripped in isolate processing. If you value it on welfare or supply-chain grounds, pay the 2-3x; if you're buying macros, the premium is noise.
- What's wrong with sucralose?
- The human evidence is mixed and the effect sizes are small. Suez et al. 2014 flagged a gut microbiome signal; subsequent trials (Ahmad 2020, Serrano 2021) showed minimal real-world impact at typical intakes. Our position: not a reason to pay 2x for a stevia-sweetened product, but if you prefer stevia or monk fruit for palate or principle, the premium options are there.
- Is plant protein a viable swap for whey?
- For trained lifters chasing MPS, only if the blend clears ~2.5-3 g leucine per serving. Pure pea and pure rice both fall short. Pea + rice blends (Banaszek 2019 trial at 48 g protein/day) matched whey on hypertrophy when total dose was high enough to brute-force leucine. Translate: you can use plant protein, but the per-dose cost to equalize leucine is ~2x whey.
- What does 'Informed Sport' mean vs 'NSF Certified for Sport'?
- Both test for WADA-banned substances at the lot level. NSF Certified for Sport additionally audits the manufacturing facility and tests for contaminants (heavy metals, prohibited compounds). For competing athletes, NSF is the stricter tier. For recreational lifters, Informed Sport is sufficient and more common.
- Why is Costco Kirkland the winner if the premium brands have better leucine numbers?
- It wins the unit-economic fight: Informed Sport tested, ~5.5 g leucine per serving, $0.013/g protein. The premium options deliver 6-7 g leucine per serving for 2-4x the price. Unless you're maxing out at a single-serving ceiling, you can hit your daily leucine target faster and cheaper with a second Kirkland scoop than with one premium scoop. The math rewards the budget pick.
A published Certificate of Analysis from a ranked brand that contradicts the label claim we scored against. An independent lab result (Clean Label, ConsumerLab) finding heavy-metal or amino-spiking failures on a current top pick. A peer-reviewed meta-analysis that shifts the leucine-per-dose threshold. Any of those triggers a dated revision within a week.
Every claim, cited.
- [01]Morton RW et al. 2018. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. Br J Sports Med 52(6):376-384.
- [02]Norton LE, Layman DK. 2006. Leucine regulates translation initiation of protein synthesis in skeletal muscle after exercise. J Nutr 136(2):533S-537S.
- [03]Moore DR et al. 2009. Ingested protein dose response of muscle and albumin protein synthesis after resistance exercise in young men. Am J Clin Nutr 89(1):161-168.
- [04]Banaszek A et al. 2019. The effects of whey vs pea protein on physical adaptations following 8 weeks of high-intensity functional training (HIFT). Sports (Basel) 7(1):12.
- [05]Clean Label Project. 2020. Protein powder investigation report: heavy metals, BPA, pesticides in 134 top-selling products.
The Larderlab Team builds evidence-led frameworks for eating, lifting, and stocking a kitchen. We cite every claim. We publish the spreadsheet when possible. We buy what we review at retail price. When new data lands, we revise with a dated note.
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