You’re standing in the kitchen, staring at that bunch of yellow fruit on the counter, and you’re wondering if it’s going to wreck your macros. It’s a classic dilemma. Bananas are basically nature’s pre-packaged snack, but they’ve developed a bit of a reputation in the low-carb world. Some people treat them like candy bars in disguise. Others swear by them for marathon fuel. Honestly, both sides have a point, but the actual amount of carbs in a banana isn't a single, static number that applies to every piece of fruit in the bowl.
Size matters. A lot.
If you grab a tiny "extra small" banana—the kind you might find in a kid's lunchbox—you’re looking at about 18 or 19 grams of carbohydrates. But if you go for the massive, foot-long monsters often found in bulk at big-box grocery stores, that number can easily soar past 35 grams. That’s a massive delta for something we just call "a banana." Most of the ones we eat fall into the "medium" category, which generally clocks in at 27 grams of carbs.
But here is where it gets interesting: your body doesn't treat all those carbs the same way.
Why the ripeness of your banana changes everything
Have you ever noticed how a green banana tastes kind of like starchy cardboard, while a brown, spotted one is basically syrup? That's not just your imagination. It's chemistry.
When a banana is green, a huge chunk of that amount of carbs in a banana is actually resistant starch. According to research published in Nutrients, resistant starch is a type of carbohydrate that your small intestine can’t actually break down. It functions more like fiber. It passes through to your large intestine where it feeds your good gut bacteria. Because you aren't absorbing it as sugar, it doesn't spike your insulin the same way.
As the fruit ripens, an enzyme called amylase starts breaking those long starch chains down into simple sugars like glucose, fructose, and sucrose.
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By the time the peel is covered in those little brown sugar spots (often called "sugar spots" for a reason), almost all that resistant starch has vanished. You’re left with quick-hitting energy. This is why endurance athletes love overripe bananas right before a race but a keto enthusiast would stay far, far away. The total carb count doesn't change much as it ripens, but the type of carb changes completely.
Breaking down the fiber factor
We can't talk about carbs without talking about fiber. A medium banana has about 3 grams of fiber. If you're someone who tracks "net carbs"—which is just total carbs minus fiber—you’d subtract those 3 grams from the total.
For that average 27-gram banana, you're looking at 24 grams of net carbs.
Is that a lot? It depends on your perspective. Compared to a slice of white bread (about 15g carbs), it’s high. Compared to a cup of cooked pasta (45g carbs), it’s modest. The fiber in the banana, particularly the pectin found in the flesh, helps slow down the digestion of those sugars, preventing the "crash" you might get from a handful of jellybeans.
The Amount of Carbs in a Banana vs. Other Fruits
People often dump bananas into the "high sugar" bucket alongside grapes and mangoes. And yeah, they aren't raspberries.
If you eat a cup of raspberries, you're only hitting about 15 grams of carbs with a whopping 8 grams of fiber. That’s the gold standard for low-carb fruit. But if you compare a banana to an apple, the gap closes. A medium apple has about 25 grams of carbs. So why do bananas get the bad rap? It’s likely the glycemic index (GI).
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A slightly underripe banana has a GI of about 42, which is considered low. A fully ripe banana jumps up to about 51 or even higher. It’s a faster fuel.
- Extra Small (under 6 inches): ~18.5g carbs
- Small (6-7 inches): ~23g carbs
- Medium (7-8 inches): ~27g carbs
- Large (8-9 inches): ~31g carbs
- Extra Large (9 inches or more): ~35g+ carbs
It's actually pretty easy to overestimate. Most people think they're eating a "medium" banana when they're actually eating a "large." If you’re being precise for medical reasons or a strict diet, weighing the fruit (without the peel!) is the only way to be 100% sure. 100 grams of banana flesh consistently delivers about 23 grams of carbs.
What about the micronutrients?
It feels wrong to just look at the amount of carbs in a banana without acknowledging what else is in there. You aren't just eating sugar. You’re getting potassium, which is vital for heart health and blood pressure regulation. You're getting Vitamin B6, which is a powerhouse for brain development and keeping your nervous system "calm."
There's also a decent hit of Vitamin C.
Most people don't realize that bananas contain dopamine and catechin, which act as antioxidants. Even though the carbs are there, they come bundled with a sophisticated delivery system of nutrients that you won't find in a processed snack bar.
Managing the carb load without giving up the fruit
If you're worried about the carb count but love the convenience of bananas, there are ways to "buffer" the hit.
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The goal is to slow down gastric emptying.
Don't eat the banana by itself on an empty stomach. That’s a recipe for a glucose spike. Instead, pair it with a fat or a protein. Smear some almond butter on it. Slice it into some full-fat Greek yogurt. The fat and protein act like a brake on your digestion, ensuring the sugar enters your bloodstream at a slow crawl rather than a sprint.
Also, consider the "half banana" rule. Half a large banana is roughly 15 grams of carbs—the same as a single serving of most carb-controlled snacks. It's often enough to kill a craving without sending your blood sugar into orbit.
The resistant starch hack
If you're really hardcore about the amount of carbs in a banana and its metabolic impact, stick to the ones with a green tint at the stem.
Green bananas have a much lower glycemic load. Some people even use green banana flour in baking because it’s so high in resistant starch. It doesn't taste like a traditional banana—it's more neutral and slightly bitter—but it's a massive win for insulin sensitivity.
Dr. Janine Higgins at the University of Colorado has done extensive work on resistant starch, noting its potential for improving gut health and increasing satiety. If you eat a greener banana, you’ll likely feel fuller for longer than if you ate a mushy, brown one.
Actionable Steps for Carb Tracking
If you're trying to integrate bananas into a health-conscious lifestyle, don't just guess. Here is the pragmatic way to handle it:
- Buy small: Specifically look for the "junior" or "snack size" bunches. They naturally limit your portion to under 20g of carbs per fruit.
- Freeze the "overripes": When bananas get too brown and the sugar content peaks, don't eat them straight. Freeze them and use small chunks in smoothies where the fiber from added spinach or protein powder can mitigate the sugar spike.
- The "Palm" Test: If the banana is longer than your hand from the base of your palm to the tip of your middle finger, count it as two servings of fruit, not one.
- Prioritize Timing: Eat your bananas around your most active times of day. Having those carbs available when your muscles are primed to soak up glucose for energy is much better than eating them right before bed.
- Check the Stem: If the stem is still firm and green, you're getting more resistant starch and less simple sugar. Aim for "barely yellow" for the best metabolic profile.
The amount of carbs in a banana doesn't have to be a dealbreaker. It’s all about context, size, and how much "green" is left on that peel. By choosing smaller, less-ripe fruit and pairing it with healthy fats, you can enjoy the convenience and nutrients of a banana without the blood sugar roller coaster.