About the Glycemic Load Calculator
Glycemic index (GI) tells you how quickly the carbohydrate in a food raises blood glucose, but not how much carbohydrate a normal portion contains. Glycemic load (GL) combines both: it multiplies the GI by the grams of available carbohydrate in the serving you actually eat and divides by 100. The result is a better guide to the blood-sugar effect of a real portion.
Use this calculator to compare foods and portion sizes — for example why watermelon has a high GI but a low GL, or how doubling a serving of rice doubles its load. It is helpful for people managing type 2 diabetes or prediabetes, low-GI dieters and athletes timing carbohydrates.
Enter the GI from a published table (such as the University of Sydney GI database) and the carbohydrate per serving from the label. Subtract fiber to get available carbohydrate, since fiber does not raise blood glucose. GI values vary with ripeness, cooking and what else is eaten with the food, so treat GL as an estimate.
With the default inputs, the glycemic load is 16.5. Change any value above to recalculate instantly.
How to use the glycemic load calculator
- 1Look up the food’s glycemic index in a GI table.
- 2Enter total carbohydrate per serving from the nutrition label.
- 3Enter fiber per serving so it can be subtracted (or 0 if already excluded).
- 4Set how many servings you eat and read the glycemic load and rating.
Formula and method
Glycemic load scales the glycemic index by the amount of carbohydrate actually eaten. Because GI is measured against 50 g of available carbohydrate compared with glucose (GI 100), dividing by 100 makes one unit of GL roughly equal to the glucose effect of 1 g of pure glucose.
A GL of 10 or less is considered low, 11–19 medium and 20 or more high. For servings the result is multiplied by the number of portions eaten. Fiber is subtracted because it is not digested into glucose.
- GL
- Glycemic load of the portion
- GI
- Glycemic index of the food (glucose = 100)
- available carbohydrate
- Digestible carbs per serving (total carbohydrate minus fiber) × servings
Worked examples
Food with GI 55 and 30 g available carbs
Total carbs of 32 g minus 2 g fiber leaves 30 g available. 55 × 30 ÷ 100 = 16.5, a medium glycemic load even though the GI itself is low.
Watermelon: high GI, small carb load
A 120 g serving of watermelon has about 6 g of carbohydrate. With a GI of 72, the GL is 72 × 6 ÷ 100 ≈ 4.3 — low, because there is little carbohydrate in the portion.
Two servings of a high-GI food
Each serving provides 44 g of available carbs, giving 73 × 44 ÷ 100 = 32.1 per serving. Eating two servings doubles the load to about 64, well into the high range.
Frequently asked questions
What is the difference between glycemic index and glycemic load?+
Glycemic index ranks how fast a food’s carbohydrate raises blood glucose compared with pure glucose. Glycemic load also accounts for how much carbohydrate is in the portion, so it reflects the real effect of what you eat.
What is a good glycemic load?+
A single food or meal with a GL of 10 or less is low, 11–19 is medium and 20 or more is high. For a whole day, a total below about 80 is generally considered low and above 120 high.
Where can I find a food’s glycemic index?+
The University of Sydney maintains the international GI database at glycemicindex.com, and published tables such as the International Tables of Glycemic Index list thousands of tested foods.
Should I subtract fiber before calculating GL?+
Yes. GI testing is based on available (digestible) carbohydrate, so fiber should be removed from total carbohydrate. In the EU and UK, labels already list carbohydrate without fiber, so enter 0 for fiber.
Is glycemic load useful for diabetes?+
Many diabetes educators use GI and GL alongside carbohydrate counting to choose foods that cause smaller glucose spikes. Total carbohydrate per meal remains the main driver, so follow your care team’s plan.
This tool gives general estimates and is not medical advice. Talk to a doctor or qualified professional about your health, diet or training.