Highest Calorie Bars UK Ranked: Per Gram & Per Bar (2026)

Written by James Frost, founder of Flaming Phoenix. Updated October 2026.

The highest calorie single bar I could verify on UK sale in October 2026 is the RealMeal bar, at about 600 calories in 150g. For chocolate, the Yorkie Duo tops the single-serve bars I checked at Tesco with 380 calories in 72g, and 90% dark chocolate is the densest at 5.9 calories per gram.

Disclosure: Flaming Phoenix makes Phoenix Bars, and they are in this comparison, with up to 557 calories in a compact, lightweight 120g bar.

How I compared them: calories per bar and calories per gram, the two numbers that decide what fits in a pocket or a pack, with protein and price added where they change the choice. Every competitor figure comes from the label shown on Tesco's website or the brand's own shop, checked October 2026.

Which bar has the most calories in the UK?

The RealMeal bar has the most calories of any single-portion bar I found on UK sale, at 600 to 604 calories in 150g, and nothing else I checked that is sold as one portion passes 557. Ranked by calories in one wrapper, single-portion bars only:

• RealMeal, Salted Caramel and Cacao & Peanut Butter (150g): 600 to 604 calories, about 30g protein, 4.0 calories per gram; £4.99 on the brand's own shop.
• Phoenix Bars (120g): 529 to 557 calories depending on flavour, up to 19g protein, 4.4 to 4.6 per gram; £5.25.
• Yorkie Duo (72g, two bars in one pack): 380 calories, 5.3 per gram; £1.30 at Tesco.
• Cadbury Starbar Duo (74g): 377 calories, 5.1 per gram; £1.35.
• Twix Xtra (75g): 370 calories, 4.9 per gram; £1.50.
• Snickers Duo (69g): 342 calories, 5.0 per gram; £1.50.
• Clif Bar, White Chocolate Macadamia (68g): 266 calories, 9.7g protein, 3.9 per gram; £2.50.
• Cadbury Starbar (49g): 249 calories, 5.1 per gram; £1.00.
• Trek Protein Flapjack, Lotus Biscoff (50g): 230 calories, 9.8g protein, 4.6 per gram; £1.85.
• Grenade Carb Killa, Chocolate Chip Salted Caramel (60g): 222 calories, 21g protein, 3.7 per gram; £2.90.

The useful finding is the gap. Nothing I checked sits between the Yorkie Duo's 380 calories and the 529 of the lightest Phoenix flavour, so if one bar has to stand in for a missed lunch, the real choice is between the top two. Phoenix Bars are the smaller bar and the one you can break into pieces or stir into porridge.

Two products sit outside the list on purpose. Greenbelly's Meal2Go, an American brand, puts 650 to 695 calories into a 155g pouch of two bars, but it is sold as a meal pack priced in dollars, so I cover it on the Greenbelly meals UK page. Sharing blocks win on size alone (a 100g Galaxy Smooth is 544 calories), so I rank them per gram below instead.

Which chocolate bar has the most calories?

Of the single-serve chocolate bars I checked on Tesco's website in October 2026, the Yorkie Duo has the most calories: 380 in a 72g pack, just ahead of the Cadbury Starbar Duo at 377. Those are two-bar packs. Among one-bar singles, the 49g Cadbury Starbar leads at 249. Whole-pack figures:

• Yorkie Duo (72g): 380 calories, 528 per 100g.
• Cadbury Starbar Duo (74g): 377 calories, 509 per 100g.
• Twix Xtra (75g): 370 calories, 493 per 100g.
• Snickers Duo (69g): 342 calories, 496 per 100g.
• Yorkie Raisin & Biscuit Duo (66g): 329 calories, 498 per 100g.
• Cadbury Boost Duo (63g): 323 calories, 513 per 100g.
• Mars Duo (69g): 305 calories, 442 per 100g.
• Cadbury Starbar (49g): 249 calories.
• Snickers (48g): 245 calories. Tesco also lists a 40g Snickers at 198.
• Kinder Bueno (43g, two fingers): 244 calories, 572 per 100g.
• Cadbury Boost (37g, from the four-pack): 190 calories.
• Mars (40g, from the four-pack): 177 calories.

Where Tesco lists half a duo pack as one serving, I have doubled it, because most people eat both. Check the weight on the wrapper before you count: the 48g Snickers was out of stock when I looked, and the 40g bar beside it has 47 fewer calories.

Mars is the least calorie-dense bar on that list at 442 per 100g, and the label shows why. Per 100g it has 70g of carbohydrate and only 16g of fat. At the standard conversion factors in UK food labelling law, 9 calories per gram of fat and 4 per gram of carbohydrate or protein, that works out as 144 + 280 + 18 = 442. A Snickers carries 25g of fat per 100g, so it reaches 496. That puts a Mars at 4.4 calories per gram.

Which bars have the most calories per gram?

Dark chocolate has the most calories per gram of any bar I checked: Lindt Excellence 90% is 592 calories per 100g, or 5.9 per gram, because 55g of every 100g is fat. The fattier the bar, the denser it is. Ranked by calories per gram:

• Lindt Excellence 90% dark (100g bar): 5.9.
• Kinder Bueno: 5.7.
• Galaxy Smooth (100g bar): 5.4.
• Yorkie Duo: 5.3.
• Cadbury Boost and Starbar: 5.1.
• Snickers: 5.0 to 5.1.
• Twix Xtra: 4.9.
• Trek Protein Flapjack and Deliciously Ella Peanut Butter flapjack: 4.6.
• Phoenix Bars: 4.4 to 4.6.
• Mars: 4.4.
• Greenbelly Meal2Go: 4.2 to 4.5.
• RealMeal: 4.0.
• Clif Bar: 3.9.
• Grenade Carb Killa: 3.7.

For a day walk, chocolate is a perfectly sensible choice, and a Yorkie Duo is 380 calories for £1.30. It gets harder over several days. Chocolate goes soft in a warm pocket and hard in the cold, a Mars has 4.5g of protein per 100g, and eating it as your main food from breakfast to dinner is hard going. Bars made for long days add protein and a texture you can still face late on. Shaun Weston, reviewing Phoenix Bars in January 2026 after a South Pole expedition, wrote: "Easy to eat, even at -45c."

If your food goes on your back, my guides to the best energy bars for expeditions, the best energy bars for ultra running and the best energy bars for hiking rank bars on the things that matter for each: cold, eating on the move and weight carried.

What protein bar has the most calories?

RealMeal is the highest calorie protein bar I could verify in the UK, with about 600 calories and 30g of protein in 150g. Most bars sold as protein bars are built the other way round, for plenty of protein and few calories:

• RealMeal: 600 to 604 calories, 30.4 to 30.6g protein.
• Phoenix Bars: up to 557 calories and up to 19g protein, which in labelling terms makes them a source of protein.
• Clif Bar: 266 calories, 9.7g protein.
• Trek Protein Flapjack: 230 calories, 9.8g protein.
• Grenade Carb Killa: 222 calories, 21g protein.

The rule I use: if you want protein with few calories, buy a protein bar such as Grenade. If you want calories with some protein included, rank by calories per bar first and treat protein as the tiebreak. For gaining weight, the best bars for weight gain page ranks these products by cost per 100 calories and by how easy they are to eat every day.

Is there a 1000 calorie bar?

No single ready-to-eat bar on UK sale reaches 1,000 calories; the biggest I found is RealMeal at about 600. At 4.6 calories a gram, the top of the Phoenix Bars range, 1,000 calories would weigh about 217g, and even at the Yorkie Duo's 5.3 it would weigh 189g. Nobody sells a single bar that heavy.

A "1000 calorie 120g protein bar" cannot exist. Pure fat is 9 calories a gram, so 120g of nothing but fat tops out at 1,080 calories, and every gram of protein or carbohydrate at 4 calories pulls the total down. Even 120g of 90% dark chocolate, the densest bar here, comes to 710.

The practical routes to 1,000 are two bars. Two Phoenix Bars give 1,058 to 1,114 calories in 240g; a RealMeal plus a Phoenix Bar gives 1,129 to 1,161 in 270g. Spread them over a morning rather than one sitting. If you would rather make your own, the homemade high calorie bars recipe shows the make-versus-buy maths.

Which high calorie bar should you choose?

Choose by the job the bar has to do, because the biggest number is not always the right one:

• Most calories and protein in one wrapper: RealMeal, if 150g in your pocket is fine.
• A compact bar you can eat whole or in pieces over a few hours: Phoenix Bars, up to 557 calories in only 120g, vegan and gluten-free.
• The cheapest calories: chocolate duos. A Yorkie Duo costs about 34p per 100 calories, against 83p for RealMeal.
• The most calories per gram for a cool day out: 90% dark chocolate or a Kinder Bueno.
• Protein with few calories: Grenade or another protein bar.
• A trail meal in a pouch: Greenbelly, an American brand priced in dollars.

If you want a bar to stand in for a meal rather than to add calories, the meal replacement bars UK guide covers the UK rules on what can be sold as a meal replacement. If you came here for the Kälteen bars from Mean Girls, the Kalteen bars page covers the film's fictional bar and the real bars closest to it, and the Japanese block gets its own Calorie Mate UK page. Our own range is on the high calorie bars homepage.

How this comparison was checked

Every competitor figure comes from a product page I opened in October 2026: Tesco's website for supermarket bars, and the brands' own shops for RealMeal and Greenbelly. Calories per bar are the label figure for the whole pack, per-gram figures are pack calories divided by pack weight, and prices are that day's shelf price before Clubcard offers. Phoenix Bars figures are our own label values. No brand paid to appear.

Recipes and pack sizes change, as the two Snickers sizes show, so the wrapper in your hand beats any list. If a figure here is out of date, tell me and I will correct it. For the wider view beyond bars, the guide to high-calorie snacks ranked by calories per gram runs the same exercise across all snack foods, and calorie-dense foods covers whole meals and ingredients.

Frequently asked questions

How many calories are in a Mars bar?

A Mars bar from Tesco's four-pack weighs 40g and has 177 calories, and the Mars Duo has 305 calories in 69g. At 442 calories per 100g, Mars is less calorie-dense than a Snickers (496) or a Galaxy (544), because it is mostly carbohydrate (70g per 100g) with only 16g of fat.

Which has more calories, a protein bar or a chocolate bar?

Gram for gram, the chocolate bar. A Grenade Carb Killa has 3.7 calories per gram (222 in 60g), while a Cadbury Starbar has 5.1 (249 in 49g). Protein bars swap fat and sugar for protein, and protein gives 4 calories a gram against 9 for fat, so they come out lower.

What is a 500 calorie bar?

It is a bar big enough to cover a small meal on its own. Only two single-portion bars I found on UK sale clear 500 calories: RealMeal at 600 to 604 in 150g and Phoenix Bars at 529 to 557 in only 120g. The next biggest I found, the Yorkie Duo, has 380.

Is chocolate the cheapest way to buy calories in a bar?

Yes, by a distance. At Tesco's shelf price a Yorkie Duo costs about 34p per 100 calories, against 83p for RealMeal, 94p for a Clif Bar and £1.31 for a Grenade Carb Killa.

Sources: label and price data from Tesco's product pages for Yorkie Duo, Cadbury Starbar Duo, Mars, Lindt Excellence 90%, Clif Bar, Grenade Carb Killa and Trek Protein Flapjack, among others; RealMeal and Greenbelly product pages; Regulation (EU) 1169/2011, Annex XIV for calorie conversion factors. All checked October 2026.