How to Calculate the Glycemic Load of a Food?

December 30, 2025 •

4 min read

According to the Linus Pauling Institute, the glycemic load (GL) combines a food's glycemic index (GI) with its carbohydrate content per serving, giving a more accurate view of its effect on blood sugar. Knowing how to calculate the glycemic load of a food is a useful method for managing blood glucose levels, particularly for individuals with diabetes or those wanting better metabolic health. This calculation provides a more complete picture than the glycemic index alone, which only measures the potential of carbohydrates to raise blood sugar without considering portion size.

Quick Summary

This article outlines the formula for calculating glycemic load (GL), using glycemic index (GI) and carbohydrate amounts. It explains the difference between GI and GL. This guide clarifies how different foods influence blood sugar. The importance of GL for dietary planning and balancing meals to improve blood glucose management is discussed.

Key Points

GL vs. GI: Glycemic load (GL) considers both the quality and quantity of carbohydrates in a food, unlike the glycemic index (GI), which only measures the potential of carbs to raise blood sugar.
The Formula: To calculate GL, multiply the food's GI by its digestible carbohydrate content per serving and divide by 100.
Example Calculation: A medium baked potato has a high GL of around 33, while a serving of lentils has a low GL of about 7.
GL Categories: Foods are classified as low GL (10 or less), medium GL (11-19), or high GL (20 or more).
Practical Application: To manage blood sugar, combine high-GI foods with low-GI foods, protein, and fiber, and control portion sizes.
Benefits of Low GL: Eating low-GL foods promotes stable blood sugar levels, provides sustained energy, and can aid in weight management.
Impact on Health: Diets high in GL are associated with an increased risk of conditions like insulin resistance and type 2 diabetes.
Reliable Data: Use reputable sources like the University of Sydney's GI database to find accurate GI values for your calculations.

Understanding the Basics: Glycemic Index vs. Glycemic Load

To calculate the glycemic load of a food, it's essential to understand the difference between the glycemic index (GI) and glycemic load (GL). The glycemic index ranks carbohydrate-containing foods based on how quickly they raise blood glucose levels after consumption. Pure glucose has a GI of 100, which is the benchmark. Foods are categorized as low (55 or less), medium (56-69), or high (70 or more) GI. However, GI alone can be misleading because it doesn't account for typical portion sizes.

For example, watermelon has a high GI of 76, but a single serving contains relatively few carbohydrates. This is where glycemic load becomes a more practical and reliable metric for daily meal planning. Glycemic load combines both the quality (GI) and quantity (portion size) of carbohydrates, providing a clearer indication of a food's overall blood sugar impact.

The Simple Formula to Calculate Glycemic Load

The calculation for a food's glycemic load is straightforward once you know two key pieces of information: the food's glycemic index and its digestible carbohydrate content per serving.

The Glycemic Load Formula

$GL = (GI \times grams \ of \ carbohydrate) / 100$

Here’s how to apply the formula step-by-step:

Find the food's glycemic index (GI): You can look up the GI value for a specific food in an international GI database, such as the one maintained by the University of Sydney. Remember that GI values can vary based on ripeness, cooking method, and processing.
Determine the grams of carbohydrates: Check the nutrition label on a packaged food to find the total carbohydrate content per serving. For whole foods, you can use a food composition table or an online nutrition calculator. Make sure to use available carbohydrates, which is total carbohydrates minus dietary fiber.
Multiply and divide: Multiply the GI value by the grams of digestible carbohydrates in your serving, then divide the result by 100.

For example, let's calculate the GL of a medium-sized baked potato. A medium baked russet potato has a GI of 111 and approximately 30 grams of carbohydrates.

$GL = (111 \times 30) / 100 = 33.3$

This result indicates a high glycemic load for a single baked potato serving. In contrast, a cup of boiled lentils has a GI of 29 and about 24 grams of available carbohydrates.

$GL = (29 \times 24) / 100 = 6.96$

This calculation shows that a serving of lentils has a low glycemic load, despite being a carbohydrate-containing food.

Categorizing Glycemic Load

Glycemic load values are typically categorized into three ranges, which help in dietary planning:

Low GL: 10 or less
Medium GL: 11 to 19
High GL: 20 or more

These categories provide a quick reference for understanding a food's potential impact on blood sugar. A diet based on low-GL foods can help in better blood sugar management, weight control, and reducing the risk of chronic diseases.

Comparison: High GL vs. Low GL Foods

Choosing foods with a lower glycemic load can lead to a slower, more gradual rise in blood sugar, preventing the rapid spikes and crashes associated with high-GL foods. This stability can help manage hunger and energy levels.


Feature	Low Glycemic Load Foods	High Glycemic Load Foods
Digestion Speed	Slow digestion and absorption, providing sustained energy.	Fast digestion and absorption, causing a rapid blood sugar spike.
Energy Levels	Stable energy levels without significant peaks or crashes.	Rapid energy boost followed by a potential crash, leading to fatigue.
Examples	Most non-starchy vegetables, legumes (beans, lentils), whole grains (oats), most fruits (apples, pears), nuts.	Refined grains (white bread, white rice), sugary drinks, cookies, cakes, potatoes.
Health Impact	Associated with better blood sugar control, weight management, and reduced risk of chronic diseases.	Associated with increased risk of insulin resistance, type 2 diabetes, and weight gain.

Practical Application of Glycemic Load in Diet

Using glycemic load in your dietary planning doesn't mean completely eliminating high-GI foods. Instead, it encourages a balanced approach by combining different food types to moderate the overall effect on blood sugar.

Here are some strategies for incorporating GL into your diet:

Pairing Foods: Eating a high-GI food with a source of protein, fiber, or healthy fat can significantly lower the overall glycemic load of the meal. For instance, pairing a slice of whole-wheat toast (medium GI) with avocado and eggs (sources of healthy fat and protein) will result in a much lower GL than eating the toast alone.
Prioritize Whole Foods: Unprocessed or minimally processed foods generally have a lower GI and GL than their refined counterparts. Opt for brown rice instead of white rice, or whole fruit instead of fruit juice.
Control Portion Sizes: Since GL is based on portion size, paying attention to how much you eat is crucial. Even a low-GI food can have a high GL if consumed in a very large quantity. Using measuring cups or a kitchen scale can help with portion control.

Conclusion

Calculating the glycemic load of a food provides a comprehensive and practical metric for understanding its effect on blood sugar levels, combining both the quality and quantity of carbohydrates. By using the simple formula—multiplying the food's glycemic index by its digestible carbohydrate content per serving and dividing by 100—you can make more informed dietary choices to promote stable blood glucose. This approach is particularly beneficial for individuals with diabetes, but it also supports healthier eating habits and weight management for everyone. Integrating low-GL foods, pairing high-GI foods with protein and fiber, and practicing portion control are all effective strategies for improving overall metabolic health. Consult a registered dietitian for personalized guidance on incorporating GL into your meal plan for the best results. [https://www.example.com/glycemic-load-resources]

Frequently Asked Questions

Glycemic index (GI) ranks carbohydrate-containing foods based on how quickly they raise blood sugar, while glycemic load (GL) provides a more complete picture by also factoring in the amount of carbohydrates in a typical serving size.

You can find GI values for thousands of foods in the international GI database, often available through the University of Sydney website. These values are based on standardized testing and are necessary for calculating GL.

Yes, cooking and processing methods can alter a food's GI and, therefore, its GL. For example, a potato's GI and GL are higher when it is baked and eaten hot compared to when it is boiled and eaten cold in a salad.

Not necessarily. A low-GI food might still be high in calories, fat, or sugar, so it is important to consider a food's overall nutritional value, not just its GI or GL. Combining foods with different GI values can also help balance a meal's impact on blood sugar.

Glycemic load is often considered a more practical tool because it accounts for portion size, which directly influences how much carbohydrate is consumed and, therefore, how much blood sugar will rise. GI alone can be misleading for foods with a high index but a low carbohydrate density, like watermelon.

You can lower a meal's glycemic load by pairing high-GI foods with protein, healthy fats, and fiber, and by controlling portion sizes. For instance, adding lentils to a rice dish or eating a piece of fruit with nuts will help regulate the blood sugar response.

Consuming foods with a high glycemic load frequently can lead to rapid blood sugar spikes, which over time may increase the risk of insulin resistance, type 2 diabetes, and weight gain. Monitoring your GL can help mitigate these risks.