The Cheapest Protein Sources in the UK, Ranked by Cost per 20g
Almost every list of the cheapest protein sources you will read is written from the gut: eggs are cheap, chicken is cheap, tofu is for people on a budget. Very few of them actually divide a price by a number of grams. So we did. We took the shelf prices at Aldi and Tesco on 8 October 2026, took protein figures from the British Nutrition Foundation, and worked out what 20g of protein actually costs from each food. Twenty grams because it is roughly what a sensible portion delivers, and it divides neatly into most daily targets. The results reorder the league table quite badly. Eggs are expensive protein. Tofu is the most expensive thing here by a mile. And the winner costs 26p.
Baked beans
A 410g tin of Aldi's Everyday Essentials baked beans costs 27p, which works out at 66p a kilo. At 5g of protein per 100g that is about 26p per 20g of protein, the cheapest thing in the shop by a clear margin. Tesco's 420g tin is 39p, or 37p per 20g, so this is one of the few items where the two shops genuinely diverge.
The obvious caveat is that nobody is building a diet on baked beans. You are buying a lot of carbohydrate and a fair amount of sugar and salt alongside the protein, and the amino acid profile is less complete than an egg's. What beans are very good at is topping up the protein in a meal that already has some, for pennies.
Tinned lentils
Aldi's Four Seasons tinned lentils are 45p for 400g, £1.13 a kilo. At 7.6g of protein per 100g that is roughly 30p per 20g. Tesco's green lentils in water are 45p for a 390g tin, £1.15 a kilo drained, and carry an Aldi Price Match label, so this one is a dead heat.
Lentils are the most useful item on this list rather than simply the second cheapest. They collapse into a sauce and thicken it, which means they can quietly raise the protein in a curry or a bolognese without anybody noticing a change in texture. Two of the recipes in our high-protein dinners round-up use exactly this trick.
Mature cheddar
A 400g block of Aldi's Emporium mature cheddar is £2.45, or £6.13 a kilo. Cheddar is 25.4g of protein per 100g, so that is about 48p per 20g. Tesco's 700g block at £4.25 comes to £6.07 a kilo and 48p per 20g, which makes cheddar one of the handful of foods that costs almost exactly the same at both shops.
Cheese rarely gets mentioned in cheap-protein lists because it is thought of as a treat rather than a protein source. On the numbers it beats chicken breast, tuna and eggs. The trade-off is saturated fat and the ease of eating 100g without really meaning to.
Tinned tuna
Aldi and Tesco both sell a four-pack of tuna chunks for £2.49, and both list it at £6.10 per kilo of drained weight. At 24.9g of protein per 100g that is about 49p per 20g at either shop.
Tuna is the most protein-dense item here relative to its calories, which is why it keeps turning up in the diet of anyone trying to eat a lot of protein without eating a lot of anything else. It is worth knowing that the per-kilo figure on the shelf edge is drained weight, so it is directly comparable with the others rather than flattered by the brine.
Greek style yogurt
A kilo of Aldi's Brooklea fat free Greek style yogurt is £1.49; Tesco's equivalent is £1.70. Here is the catch that the marketing does not help with: Greek style yogurt is not strained Greek yogurt, and the British Nutrition Foundation puts plain Greek-style yogurt at just 5.7g of protein per 100g. That works out at about 52p per 20g at Aldi and 60p at Tesco.
So the tub that feels like a protein food is middling value, and the gap between the two shops is real at 14%. Properly strained Greek yogurt, and the high-protein skyr-style tubs, carry two or three times the protein and are worth checking the label on rather than assuming.
Chicken breast
Aldi's cheapest chicken breast is the 2kg pack of Ashfields fillets at £12.29, or £6.15 a kilo. Tesco's cheapest own-brand equivalent is the 1.6kg Large Chicken Fillet Pack at £10.65, £6.66 a kilo. Raw chicken breast carries about 230g of protein per kilo once you account for cooking losses, which puts it near 53p per 20g at Aldi and 58p at Tesco.
The more interesting number is the cut you did not buy. Bone-in chicken thighs are £2.99 a kilo at both shops, less than half the price of breast, and Tesco price-matches Aldi on them to the penny. Thigh is slightly lower in protein and has more fat, but no reasonable protein-per-pound calculation favours breast.
Eggs
This is the result that surprised us. Aldi's medium free range eggs are £2.49 for a dozen, 21p each; Tesco's are £2.85, 24p each. A medium egg gives you roughly 7g of protein, so a 20g serving is nearly three eggs and costs about 60p at Aldi and 68p at Tesco.
That makes eggs more expensive protein than chicken breast, tuna and cheddar, which is the opposite of their reputation. Eggs are still excellent food, genuinely convenient and one of the most complete proteins you can buy. They are simply not the budget option everyone assumes, and the gap has widened as egg prices have risen faster than chicken.
Firm tofu
Aldi's Plant Menu organic super firm tofu is 95p for 200g, £4.75 a kilo. Tesco's Plant Chef organic firm tofu is £1.95 for 399g, £6.50 a kilo of drained weight. Using the British Nutrition Foundation's figure of 8.1g of protein per 100g, that is roughly £1.17 per 20g at Aldi and £1.60 at Tesco — between two and four times the cost of everything above it.
One honest qualification: tofu varies more than any other food here. The 8.1g figure is for steamed tofu, and extra-firm blocks can carry half again as much protein, which would pull the cost down accordingly. Even on a generous reading, though, tofu is not the cheap protein it is widely assumed to be. It earns its place on taste, texture and not being meat, not on price.
The useful conclusion is not that everyone should eat baked beans. It is that the cheapest protein sources are rarely the ones with the protein marketing, and that a tin of lentils stirred into something you were cooking anyway does more for your weekly protein and your budget than switching supermarket does. Remy prices a recipe's whole shopping list across the supermarkets you actually use, so you can see what a meal costs before you buy it rather than after.
Frequently asked questions
What is the cheapest source of protein in a UK supermarket?
Tinned pulses. Baked beans came out at roughly 26p per 20g of protein at Aldi and tinned lentils at about 30p, which is less than half the cost of chicken breast, tuna or cheddar. The trade-off is that you are buying a lot of carbohydrate alongside the protein.
Are eggs cheap protein?
Less than you would think. At 21p an egg and about 7g of protein each, 20g of protein costs around 60p, which puts eggs behind chicken breast, tuna and cheddar on cost. They are still convenient and nutritionally excellent, just not the budget pick.
Does it matter whether I shop at Aldi or Tesco?
Less than you would expect on protein staples. Tesco price-matches Aldi on chicken thighs, beef mince, tinned tuna, tinned lentils, chickpeas and peanut butter, so those cost the same at both. The gap shows up on own-brand yogurt, eggs, baked beans and tofu.
Should I just eat the cheapest protein on the list?
No. Cheapest per gram is a useful tiebreaker, not a diet plan. Pulses have a less complete amino acid profile than meat, fish, dairy or eggs and come with a lot of carbohydrate, so they work best topping up meals that already contain some protein rather than replacing them.
How long will these prices be accurate?
Not very. They were read off Aldi and Tesco's own listings on 8 October 2026 and grocery prices move constantly. The ordering is far more durable than the exact figures: pulses have been the cheapest protein for years and are likely to stay there.