The short answer
A medium banana, about 18 to 20 centimetres long, has roughly 100 to 110 calories. A small banana is closer to 90 calories and a large one around 120 to 135. Almost all of those calories come from carbohydrate, with a little protein and very little fat. A medium banana also provides around 3 grams of fibre and is a well-known source of potassium.
That makes a banana a convenient, portable snack that is easy to estimate. The main thing to get right is the size.
Banana calories by size
Bananas vary a lot in size, and the weights below refer to the edible fruit without the peel. Supermarket bananas are often medium to large.
| Size | Approx. length | Edible weight | Approx. calories | Carbs |
|---|---|---|---|---|
| Extra small | under 15 cm | about 80 g | 70–75 | 18 g |
| Small | 15–18 cm | about 100 g | 85–95 | 23 g |
| Medium | 18–20 cm | about 118 g | 100–110 | 27 g |
| Large | 20–23 cm | about 136 g | 120–125 | 31 g |
| Extra large | over 23 cm | about 152 g | 130–140 | 35 g |
If you are unsure, logging a banana as medium is a reasonable default. If you want to be more precise, weigh one peeled banana once; you will quickly learn how the bananas you usually buy compare.
What is in a banana
Carbohydrate and sugar
A medium banana contains around 27 grams of carbohydrate. As a banana ripens, more of its starch turns into sugar, which is why a spotty banana tastes sweeter than a green-tinged one. The calories stay roughly the same; what changes is the balance between starch and sugar. The sugar in whole fruit is not counted as "free sugar" in common public health guidance, because it comes packaged with fibre and water.
Fibre
A medium banana provides around 3 grams of fibre. Slightly less ripe bananas contain more resistant starch, a type of carbohydrate that behaves a bit like fibre. Fibre is linked to better digestion and feeling full.
Vitamins and minerals
Bananas are known for potassium, with a medium banana providing roughly 400 milligrams. They also contain vitamin B6, vitamin C and some magnesium. Like all fruit, a banana counts as one portion toward the commonly recommended five a day.
Protein and fat
A banana has only about 1 gram of protein and very little fat. If you want a snack that keeps you full for longer, pairing a banana with something that contains protein can help.
Banana products and dishes
Once bananas are processed or combined with other ingredients, the calories can change a lot:
- Banana chips are usually fried, so a small 30-gram handful can be around 150 calories, more than a whole fresh banana.
- Dried banana without frying is concentrated, so it is easy to eat more than you would fresh.
- Smoothies often contain one or two bananas plus milk, yoghurt, nut butter or juice, which adds up quickly.
- Banana bread is closer to cake, and a thick slice is often 250 to 350 calories or more.
Simple ways to make a banana more filling
A banana on its own is light, which is great for a quick bite but may not hold you for long. Some easy pairings:
- A banana with a pot of plain yoghurt or skyr.
- Sliced banana on porridge or overnight oats.
- Banana with a small handful of nuts or a teaspoon of nut butter.
- Banana with a glass of milk or a soya drink.
For more ideas in a similar range, see our list of low-calorie snacks, and for pairing carbohydrate with protein through the day, our guide to foods for steady energy.
Bananas and exercise
Bananas are a popular snack before or during exercise because they are easy to carry, easy to digest for most people, and provide carbohydrate. Whether you need a snack before a workout depends on how long and hard you are training and when you last ate.
Frequently asked questions
Are bananas fattening?
No single food causes weight gain on its own. A medium banana has around 100 to 110 calories, very little fat and some fibre, so it fits easily into most eating patterns.
Do riper bananas have more calories?
Not meaningfully. As bananas ripen, starch turns into sugar, so they taste sweeter, but the total calories stay roughly the same.
How many bananas a day is okay?
For most healthy people, one or two bananas a day is a common amount as part of a varied diet. If you have a kidney condition or have been told to limit potassium, follow your doctor's advice.