How Much Potato is 20 Carbs? Understanding Serving Size

November 6, 2025 •

3 min read

A 100-gram portion of boiled potato contains approximately 20.1 grams of carbohydrates, indicating that a relatively small amount of this starchy vegetable can contribute significantly to your daily carb count. Knowing precisely how much potato is 20 carbs is essential for those monitoring their intake for weight management, diabetes, or a low-carb diet like keto.

Quick Summary

This guide provides a precise breakdown of how much potato provides 20 grams of carbohydrates, including how different cooking methods and potato varieties can alter the carbohydrate content. It covers practical portion control strategies and alternatives for managing carb intake.

Key Points

100g of Boiled Potato is approximately 20 Carbs: A 100-gram (3.5oz) serving of plain, boiled white potato provides roughly 20.1 grams of carbohydrates, including fiber.
Cooking Method Affects Density: Baking and frying concentrate carbohydrates by removing water or adding oil, meaning a smaller weight of cooked potato will contain 20 grams of carbs compared to boiled.
Potato Variety Matters: White, sweet, purple, and russet potatoes have slightly different carb counts per 100g, so checking specific nutrition facts is best for accuracy.
Portion Control is Key: For precise carb counting, always weigh your cooked potatoes with a food scale rather than estimating volume.
Low-Carb Alternatives Exist: Vegetables like cauliflower, swede, turnips, and daikon radish are excellent low-carb substitutes that can be prepared in potato-like dishes.
Resistant Starch can Lower GI: Cooling cooked potatoes before eating increases resistant starch, which can lower their glycemic index and slow carb absorption.

Calculating Your 20-Carb Potato Portion

Determining the exact amount of potato for a 20-carb serving depends on the potato's variety and cooking method. The carbohydrate content is not uniform, as factors like water loss during cooking can concentrate nutrients. A standard 100-gram (approx. 3.5 ounces) serving of boiled white potato is a good baseline, as it contains about 20.1 grams of carbohydrates. However, to be more precise, it's helpful to consider the weight in its cooked form.

For example, based on standard nutrition data, a 100-gram serving of boiled potato (without salt) contains just over 20 grams of carbs. If you are working with raw potatoes, you might need a slightly larger piece to account for water loss during cooking. One study on potatoes found that the average raw potato contains about 17.5 grams of carbs per 100 grams, meaning a raw portion closer to 115 grams would be needed to hit the 20-gram mark.

The Impact of Preparation on Carb Content

How you prepare a potato significantly affects its nutritional profile, particularly the carbohydrate concentration. For instance, while boiling may slightly reduce some nutrients, it doesn't dramatically change the carb content per 100 grams, especially if cooked with the skin on. However, processes like mashing or frying introduce other variables.

Boiling: A 100g serving of plain boiled potato contains about 20.1g of carbohydrates.
Baking: Baking a potato causes water to evaporate, concentrating the nutrients. A 100g portion of a baked potato will have a higher concentration of carbs than a boiled one of the same weight.
Mashing: Mashing breaks down the starch structure, increasing the rate of absorption and the glycemic index (GI), but the total carb content per serving remains similar to boiled potatoes. Adding milk or butter will increase total calories and may slightly increase the carb count.
Frying: Frying, especially in oil, increases the fat and calorie count dramatically. A 100g portion of fried potatoes will have a different macronutrient ratio, with a potentially higher carb concentration depending on water loss.

Comparing Potato Varieties for 20 Carbs

Not all potato varieties are created equal when it comes to carbohydrate content. While the differences may be slight per 100g, they can add up, especially if you are tracking precisely. Here is a comparison of what approximately 20 grams of carbs looks like across a few common types based on a 100g serving size:


Potato Variety	Carbohydrates per 100g	Estimated 20g Carb Serving	Notes
White Potato	~21 grams	~95 grams	Slightly fewer carbs per gram than some others.
Sweet Potato	~22 grams	~91 grams	Orange flesh provides higher Vitamin A, slightly more carbs.
Purple Potato	~21 grams	~95 grams	High in antioxidants (anthocyanins).
Russet Potato	~20-21 grams	~95-100 grams	Common baking potato, standard carb count.

Strategies for Portion Control and Low-Carb Swaps

For those watching their carb intake, using a food scale is the most accurate method to ensure you don't exceed your target. Instead of eyeballing a serving, weigh your cooked potato to guarantee a 20-carb portion. Another effective strategy is to use potatoes as a complement rather than the central component of a meal.

For low-carb or keto dieters, finding suitable alternatives is key to reducing overall carb intake. Here are a few options:

Cauliflower: Can be mashed, roasted, or riced as a versatile, low-carb replacement for potatoes. A cup of mashed cauliflower contains just 5 grams of carbs.
Swede (Rutabaga): Can be baked or roasted as a low-carb alternative.
Turnips: Sliced and baked, they can mimic scalloped potatoes.
Daikon Radish: Boiled and roasted, it makes a convincing gratin.
Zucchini: Spiralized zucchini noodles are an excellent substitute for pasta but can also be served with potato-style sauces.

Conclusion

Understanding how much potato is 20 carbs is crucial for mindful eating, especially when managing specific dietary needs. While a 100g portion of boiled potato serves as a reliable benchmark, considering the variety and cooking method offers a more precise approach. Using a food scale, practicing portion control, and exploring low-carb alternatives can help you enjoy potatoes responsibly while staying within your nutritional goals. Regardless of your approach, potatoes offer a nutrient-dense source of energy, and with careful planning, they can certainly fit into a balanced diet. More information on potato nutrition can be found on websites like the Potato Goodness site.

Frequently Asked Questions

The cooking method doesn't change the absolute carb content of a raw potato, but it affects the concentration. For example, a baked potato loses water, so a smaller cooked portion contains the same number of carbs as a larger raw one. Frying adds fat and calories but also concentrates carbs.

A medium baked potato (around 173g or 6.1oz) can contain approximately 36.6 grams of carbohydrates. This shows that a whole medium potato is significantly more than 20 carbs.

No, sweet potatoes are not necessarily lower in carbs. Per 100g, sweet potatoes and white potatoes have a similar carbohydrate content. A medium white potato has about 26g of carbs, while a medium sweet potato has around 23g.

Some low-carb and ketogenic diets restrict potatoes because they are a starchy vegetable, and their high carbohydrate content can quickly consume a person's daily carb limit. However, in moderation, potatoes can be part of a healthy diet.

The Glycemic Index (GI) of potatoes can vary widely depending on the variety and how they are prepared. It can range from medium to high. Cooling cooked potatoes can lower their GI by increasing resistant starch.

Yes, you can increase the resistant starch content by cooking potatoes and then cooling them in the refrigerator for 12-24 hours. This can help lower their glycemic impact when you later eat them cold or lightly reheated.

For better blood sugar control, opt for waxy varieties, boil or steam them, and consider cooling them before serving. Pairing potatoes with protein and healthy fats also helps to slow digestion and balance blood sugar levels.