How many calories in a banana?
A medium banana is about 105 calories — but "a banana" isn't one number. The real range runs from roughly 72 for an extra-small one to 135 for an extra-large, and the supermarket bananas most people actually buy sit at the larger end. Pick your size below.
Based on 89 kcal per 100 g of edible flesh (USDA). The skin is roughly a third of the whole-fruit weight, but you don't eat it, so it never counts.
The changeover point — starch is converting to simple sugars as it ripens.
Calories: unchanged. Ripening rearranges the carbohydrate — it doesn't add energy.
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Why the number you saw is probably wrong
Most quick answers quote a single figure — often "89" (the per-100 g lab value) or "105" (a medium fruit) — and the two get mixed up constantly. A medium banana weighs around 118 g of edible flesh, so at 89 kcal per 100 g it lands near 105 calories. A small one (≈101 g) is about 90; a large one (≈136 g) is about 121. The single biggest source of error is just guessing the wrong size: shop bananas are frequently "large", not "medium".
Ripeness changes the sugar, not the calories
A green banana is roughly 80% starch — much of it resistant starch, which passes through to the large intestine and feeds gut bacteria instead of spiking blood sugar. As the fruit yellows and spots, enzymes convert that starch into simple sugars, until a heavily spotted banana is around 80% sugar and almost no starch. Despite the dramatic chemistry, the total calories stay essentially the same — what shifts is sweetness, digestion speed and glycaemic impact, not energy. That's why brown bananas are the bakers' choice.
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What else is in it
A medium banana carries about 27 g of carbohydrate, ~14 g of naturally occurring sugar, ~3 g of fibre, ~1.3 g of protein and essentially no fat. Its headline nutrient is potassium — roughly 422 mg, about 9% of a day's needs — though, per 100 g, a baked potato or cooked spinach actually beats it. Freezing a banana for smoothies changes the texture to something ice-cream-like but leaves the calorie count untouched.
A banana is not banana bread
If you searched "calories in a banana" on your way to banana bread, the numbers part company fast. A single slice of banana bread is commonly 196–250+ calories — most of that from the added sugar, butter and flour, not the fruit. The banana is the smallest part of the equation; the recipe is the rest.
The banana you're counting is a clone
Nearly every banana traded worldwide is a Cavendish — a single genetic clone. It replaced the sweeter Gros Michel in the 1950s after Panama disease wiped that variety out of commercial trade, and the Cavendish now faces the same fungal threat (Tropical Race 4). The calorie count on this page describes one specific cloned cultivar, grown at scale precisely because it ships well.
Common questions
- USDA FoodData Central — banana, raw: 89 kcal, 22.8 g carbohydrate, 12.2 g sugar, 2.6 g fibre, 358 mg potassium per 100 g.
- Healthline — calories by size: extra small ~72, small ~90, medium ~105, large ~121, extra large ~135.
- Harvard T.H. Chan School of Public Health, The Nutrition Source — a medium banana ~110 kcal, 28 g carbohydrate, 15 g sugar, 3 g fibre, 422 mg potassium.
- CalorieKing — 99 kcal per 110 g medium banana, edible portion.
So there's no single right answer — only the right answer for the banana in your hand. Weigh it, or pick its size above, and the calculator does the rest.