I've spent over a decade working with fruit nutrition, and one question keeps coming up: what are the actual macronutrients of a banana?
Let me give you the straight answer.
A medium banana (about 118g) contains approximately 27g of carbohydrates, 1.3g of protein, and 0.4g of fat.
It's basically a carb fruit with trace amounts of the other macros.
But here's what most people miss: those numbers shift depending on ripeness, and that matters more than you'd think.
The Macronutrient Breakdown of a Banana
The macros change with banana size, so let's break it down properly.
Small banana (101g):
- Carbohydrates: 23g
- Protein: 1.1g
- Fat: 0.3g
- Total calories: 90
Medium banana (118g):
- Carbohydrates: 27g
- Protein: 1.3g
- Fat: 0.4g
- Total calories: 105
Large banana (136g):
- Carbohydrates: 31g
- Protein: 1.5g
- Fat: 0.5g
- Total calories: 121
You're looking at roughly 89% carbohydrates, 4% protein, and 3% fat by calorie distribution.
That remaining 4% comes from water and other compounds.
The protein and fat content is negligible, which is why bananas aren't your go-to for those macros.
Carbohydrates: The Dominant Macro
Here's where it gets interesting.
Those 27g of carbs in a medium banana aren't all the same type.
You've got about 14g of natural sugars (glucose, fructose, and sucrose), roughly 6g of starch, and 3g of dietary fiber.
The fiber counts toward your total carb number, but your body processes it differently.
It doesn't spike your blood sugar like simple sugars do.
It slows digestion, feeds your gut bacteria, and helps with satiety.
The carb breakdown looks like this:
- Simple sugars: 14g (quick energy)
- Starch: 6g (slower-releasing energy)
- Fiber: 3g (digestive benefits, no calorie absorption)
Your net carbs (total carbs minus fiber) sit around 24g for a medium banana.
That's what most people tracking macros for keto or low-carb diets actually care about.
In a large banana, you're looking at higher numbers across the board, but the macro ratio stays similar.
Resistant Starch: The Hidden Macro Player
Here's something most macro counters miss.
Greener bananas contain resistant starch, a type of carbohydrate that behaves more like fiber than sugar.
It resists digestion in your small intestine and ferments in your large intestine instead.
Your body doesn't fully absorb the calories from resistant starch.
A green banana might have 4-5g of resistant starch, which technically counts as carbs on paper but doesn't impact your blood sugar the same way.
As the banana ripens, enzymes break down that resistant starch into simple sugars.
That's why ripe bananas taste sweeter and hit your bloodstream faster.
How Ripeness Changes the Macros
The total macro numbers barely change as a banana ripens.
What changes is the type of carbohydrate, and that's crucial.
Green banana (underripe):
- Total carbs: ~27g
- Resistant starch: 4-5g
- Simple sugars: 8-9g
- Glycemic impact: Lower
Yellow banana (ripe):
- Total carbs: ~27g
- Resistant starch: 1-2g
- Simple sugars: 14-15g
- Glycemic impact: Medium
Spotted banana (very ripe):
- Total carbs: ~27g
- Resistant starch: <1g
- Simple sugars: 16-17g
- Glycemic impact: Higher
The macro label stays the same, but your body handles these differently.
Green bananas keep you fuller longer because that resistant starch acts like fiber.
Ripe bananas give you faster energy because the sugars are readily available.
I've seen people tracking macros get frustrated because they don't account for this shift.
A green banana and a spotted banana both clock in at 27g carbs, but the metabolic response isn't identical.
For macro tracking purposes, the ripeness factor matters if you're managing blood sugar or timing carbs around workouts.
Protein and Fat in Bananas
Let's be honest about the other macros.
Bananas are rubbish for protein and fat.
That 1.3g of protein in a medium banana is barely 3% of your daily needs (based on a 50g target).
The 0.4g of fat is about 0.5% of a standard 70g daily fat intake.
You're not eating bananas for these macros.
The protein in bananas is incomplete anyway, missing some essential amino acids your body needs.
The tiny amount of fat is mostly polyunsaturated and monounsaturated, with trace amounts of saturated fat.
It's not enough to matter nutritionally.
If you're trying to balance your macros across a meal, you'll need to pair bananas with actual protein and fat sources.
Peanut butter with a banana is popular because it adds roughly 8g protein and 16g fat to balance out those banana carbs.
Greek yogurt works too, giving you 15-20g protein to offset the carb load.
What These Macros Mean for Your Diet
Now for the practical bit.
For Low-Carb and Keto Diets
A medium banana's 24g net carbs will blow through most keto macro limits in one go.
Standard keto caps carbs at 20-50g daily.
One banana and you're done.
If you're doing low-carb (50-150g daily), a banana fits, but it takes up a significant chunk of your carb budget.
Frozen bananas have the same macros as fresh, so freezing doesn't help you here.
For Athletes and Active People
Those 27g of carbs are perfect pre-workout or post-workout fuel.
The mix of fast-acting sugars and slower starch gives you both immediate and sustained energy.
Athletes often time banana consumption around training because of this macro profile.
Quick energy without needing protein or fat to slow digestion.
The fiber content means you won't crash as hard as you would with pure sugar.
For Weight Loss
The macros tell one story, but satiety tells another.
Yes, 105 calories from mostly carbs seems like a lot for one piece of fruit.
But that 3g of fiber and the resistant starch in less-ripe bananas actually help you feel full.
The key is tracking those macros accurately and fitting them into your daily targets.
Don't eat three bananas thinking they're "free" because they're fruit.
Those carbs add up fast.
For Balanced Eating
If you're not tracking macros religiously, bananas fit fine into a balanced diet.
They're predominantly carbs, so pair them with protein and healthy fats.
Banana with almond butter, banana in a protein smoothie, banana sliced over oatmeal with nuts.
Balance the macros across the meal, not within the banana itself.
Conclusion
The macronutrients of a banana are straightforward: roughly 27g carbs, 1.3g protein, and 0.4g fat in a medium-sized fruit.
It's a carbohydrate food with minimal protein and fat.
What makes it interesting is how ripeness shifts the type of carbs without changing the total macro count, and how that 3g of fiber affects digestion and satiety despite being lumped into the carb total.
Track your banana macros accurately, account for size differences, and remember those numbers when planning your meals around the macronutrients of a banana.
