How many carbs are in a potato?
One medium raw potato has about 37g of carbohydrate and 33g of net carbs. How you cook it changes the glycemic index significantly, though not the carb count.
Carbs by portion
| Portion | Total carbs | Fiber | Net carbs |
|---|---|---|---|
| 1 medium potato, raw (213g) | 37.3g | 4.5g | 32.8g |
| 1 Potato small (170g) | 29.7g | 3.6g | 26.2g |
| 1 Potato large (369g) | 64.5g | 7.7g | 56.8g |
| 1 cup, diced (75g) | 13.1g | 1.6g | 11.5g |
| 100 grams | 17.5g | 2.1g | 15.4g |
Net carbs
One medium raw potato has about 33g of net carbs, which is total carbs (37g) minus fiber (4g). Most of that fiber is in the skin. Peeled potatoes have fewer net carbs from fiber and digest more quickly. See the net carbs guide.
Glycemic index of a potato
The glycemic index of a potato is about 78. Boiled potatoes (with skin) have a GI around 78. Mashed potatoes run even higher at about 87. Cooling boiled potatoes before eating converts some starch to resistant starch, lowering the GI to the 50s. Frying in fat adds calories but actually lowers the GI somewhat.
For diabetes
One medium potato is about 37g of carbs with a high GI of 78 when boiled. The glucose rise is fast and significant. Eating potato with the skin on, cooling it before serving, or pairing it with vinegar, fat, or protein all meaningfully lower the glycemic response. For many people with diabetes, half a medium potato (about 18g of carbs) with protein and non-starchy vegetables is a more manageable portion than a whole one. See the diabetes carb-counting guide.
Keto and low carb
One medium potato has about 33g of net carbs, well over a full strict keto day's budget. Potatoes do not fit keto. Cauliflower is the standard substitute for mashing, and radishes or turnips can substitute in roasted dishes.
Good to know
Cooking method dramatically affects how a potato behaves. A boiled, cooled potato has a GI around 56 (resistant starch forms on cooling). A freshly mashed potato has a GI of 87. French fries are around 63 due to the fat content. Leaving the skin on preserves the 2g of fiber in the skin, which slows digestion slightly. A raw potato is toxic due to solanine, so all the GI data above refers to cooked potato.
Full nutrition (per 100g)
- Calories: 77.0 kcal
- Carbohydrate: 17.49g
- Fiber: 2.1g
- Sugars: 0.82g
- Protein: 2.05g
- Fat: 0.09g
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Get the appFrequently asked questions
How many carbs are in a potato?
One medium potato (213g) has about 37g of carbohydrate. A small potato (170g) has about 30g. A large potato (369g) has about 65g.
Does cooking change a potato's carbs?
Total carbs stay the same regardless of cooking method. But cooling a boiled potato converts some starch to resistant starch, lowering the glycemic response. Mashing produces the fastest blood sugar rise.
Is a potato keto?
No. One medium potato has about 33g of net carbs, exceeding a full strict keto day's budget.
What is the glycemic index of a potato?
A boiled potato has a GI around 78. Mashed potato is about 87. A boiled potato cooled and reheated drops to the 50s due to resistant starch.
Is potato better or worse than rice for blood sugar?
Comparable. Both have high GIs when freshly cooked. Potato has more fiber per serving. Neither is low-glycemic, and both require portion control for blood sugar management.