How many calories are in a banana?
A medium banana — roughly 120 g of peeled fruit — is about 105 kcal. The flesh runs about 90 kcal per 100 g, so once you know the weight you know the number; the trouble is that “a banana” covers a range of nearly two to one.
Per portion
| Portion | Calories | Protein | Carbs | Fat |
|---|---|---|---|---|
| Small, ~80 g peeled (15 cm / 6 in) | ~70 | 0.9 g | 19 g | 0.3 g |
| Medium, ~120 g peeled (18 cm / 7 in) | ~105 | 1.3 g | 27 g | 0.4 g |
| Large, ~135 g peeled (20 cm / 8 in) | ~120 | 1.5 g | 31 g | 0.4 g |
| Extra large, ~150 g peeled | ~135 | 1.7 g | 35 g | 0.5 g |
| 100 g peeled flesh | ~90 | 1.1 g | 23 g | 0.3 g |
| Sliced, 1 cup (~150 g) | ~135 | 1.7 g | 34 g | 0.5 g |
The skin is roughly a third of the whole weight, so a banana reading 150 g unpeeled is about 100 g of fruit — about 90 kcal, not 135.
What changes the number
Size, overwhelmingly. Small to extra-large is 70 to 135 kcal. Two a day at the top of that range rather than the bottom is about 130 kcal.
Variety. The small, intensely sweet types — elaichi or yelakki, lady finger — are often only 50–70 kcal each, because they are 60–80 g of fruit. Plantain and other cooking bananas are denser raw and almost always fried, which is where their calories actually come from.
Drying and frying. Banana chips are not bananas. Fried in coconut oil they run close to 500 kcal per 100 g, so a 30 g handful beats the whole fresh fruit in a fraction of the volume. Even unfried dried slices are around 350 kcal per 100 g, because the water is gone.
What you put with it. A banana shake with 250 ml of whole milk, sugar and a scoop of ice cream is 350–500 kcal. Two tablespoons of peanut butter adds about 190. The fruit is rarely the expensive part.
Where it fits in a deficit
At about 90 kcal per 100 g, bananas sit in the low-density band — denser than berries or melon, lighter than anything baked. The portion is self-limiting in a way a packet is not, and the fibre and water hold better than a cereal bar of the same calories.
Protein is negligible at 1.3 g, so this is a carbohydrate snack, not a meal. It works well as fuel before training, where density is an advantage rather than a trap — the same reasoning that makes a measured serving of brown rice a sensible pre-session carbohydrate.
Ripeness changes the sugar, not the calories
A green banana is mostly starch, a good share of it resistant starch. As it ripens, enzymes convert that starch into sucrose, glucose and fructose — the banana gets sweeter and softer, and the carbohydrate is the same carbohydrate, rearranged.
Total energy barely moves. A very green banana may deliver a few kcal less than a spotted one of the same weight, since resistant starch is incompletely digested, but the difference is single digits, not 30 or 40 kcal. Green bananas raise blood glucose more slowly and some people find them more filling; neither is a calorie saving.
“Bananas are fattening”
They are not, and the claim does not survive the numbers. A medium banana is about 105 kcal — roughly a large apple, well under a 30 g handful of almonds (~175 kcal), and half a 500 ml cola (~210 kcal). The sugar figure that alarms people is around 14 g in a medium banana, comparable to an apple or a pear, and it arrives with 2.6 g of fibre and about 75% water rather than on its own.
The related rules — no bananas at night, avoid them for their glycaemic index, one a day maximum — have nothing behind them. The arithmetic of a calorie deficit does not care what hour the fruit was eaten in. If the worry came from a banana-flavoured product, reading its label properly is the more useful exercise.
Figures are typical values and vary by variety, size and preparation. General information, not medical advice.