Lentils (cooked) vs Peanut butter: which protein is cheaper?

Budget says one, calories say the other

Peanut butter costs $0.022 per gram of protein against $0.022, so it saves $0.16 a week at a 100 g/day target. Lentils (cooked) answers a different question: 7.8 g of protein per 100 kcal against 4.3 g, which is what matters once calories, not dollars, are the thing you run out of first.

The amount you actually have to eat

Thirty grams of protein means 333 g of lentils (cooked), against 120 g for peanut butter. That is a real constraint, not a footnote: a price per gram only counts if the serving is one a person will finish. Treat lentils (cooked) as the base of a meal that other protein is added to, not as the protein itself.

What the calories cost you

Getting 30 g of protein from peanut butter brings 706 kcal with it. On a 2,000 kcal day, three servings would be most of your budget before anything else goes on the plate. That is fine when you are eating at maintenance or building, and it is the reason this food falls apart on a cut no matter how good the price per gram looks.

Two budget staples, so the tiebreak is elsewhere

Both of these sit in the cheapest third of everything we track (#8 and #7 of 25), and the difference between them is $0.01 per 30 g of protein. That is small enough that shelf life, prep time and whether you will actually eat it should decide this, not the price column.

Compare against other foods

• Lentils (cooked) vs Oats (dry)Peanut butter vs Oats (dry)
• Lentils (cooked) vs Tofu (firm)Peanut butter vs Tofu (firm)
• Lentils (cooked) vs Black beans (cooked)Peanut butter vs Black beans (cooked)
• Lentils (cooked) vs Whey protein (1 scoop)Peanut butter vs Whey protein (1 scoop)
• Lentils (cooked) vs Greek yogurt (nonfat)Peanut butter vs Greek yogurt (nonfat)
• Lentils (cooked) vs Eggs (~2 large)Peanut butter vs Eggs (~2 large)
• Lentils (cooked) vs Chicken breast (raw)Peanut butter vs Chicken breast (raw)
• Lentils (cooked) vs Canned tuna (in water)Peanut butter vs Canned tuna (in water)

Frequently asked

Which is cheaper for protein, lentils (cooked) or peanut butter?

Peanut butter, at $0.022 per gram of protein against $0.022 for lentils (cooked) (July 2026 US grocery prices). A 30 g protein serving costs $0.66 vs $0.67.

Which has more protein per calorie, lentils (cooked) or peanut butter?

Lentils (cooked), with 7.8 g protein per 100 kcal against 4.3 g for peanut butter, 1.8x leaner. That matters when you are cutting and calories are the binding constraint.

Which should I buy, lentils (cooked) or peanut butter?

Depends on your constraint. On a tight budget with room in your calories, peanut butter is cheaper per gram of protein. On a calorie-capped cut, lentils (cooked) gives you 1.8x more protein per calorie and is usually worth its $0.022/g price.