Meal Glycemic Index Calculator
The glycemic index (GI) of a mixed meal can be estimated by weighting each food's GI value by its proportional contribution to total available carbohydrates in the meal. This method was defined by the FAO/WHO Expert Consultation on Carbohydrates in Human Nutrition and is used in nutrition research and dietary planning. Enter up to four foods with their GI values and available carbohydrate grams; the calculator weights each food's GI by its carb share and sums them to give the meal's overall weighted GI. It also calculates the glycemic load (GL = weighted GI * total carbs / 100), which accounts for portion size.
Enter each food: GI value (0-100) and available carbohydrates in grams.
Weighted GI formula
Weighted GI = sum(GI(i) * Carbs(i)) / sum(Carbs(i))
Glycemic Load (GL) = Weighted GI * Total Carbs / 100
Each food's GI is multiplied by its carbohydrate grams, the products are summed, and divided by total carb grams. GL further adjusts for portion size: low GL is below 10, medium is 11-19, high is 20 or above.
GI categories and meal planning
- Low GI (55 or below): oats, lentils, most fruits and vegetables, basmati rice.
- Medium GI (56-69): whole wheat bread, brown rice, couscous, new potatoes.
- High GI (70 or above): white bread, most breakfast cereals, white rice, baked potatoes.
- Combining high-GI foods with protein, fat, fiber, and low-GI foods lowers the overall meal GI.
- Glycemic load is more useful than GI alone because it accounts for realistic serving sizes.
Meal glycemic index calculator: frequently asked questions
What is the glycemic index (GI)?
The glycemic index ranks carbohydrate-containing foods on a scale of 0-100 based on how much they raise blood glucose compared to pure glucose (GI = 100) or white bread. Low GI is 55 or below, medium GI is 56-69, and high GI is 70 or above.
How is the GI of a mixed meal calculated?
The weighted GI of a meal is calculated by summing the products of each food's available carbohydrate grams and its GI, then dividing by the total available carbohydrate grams in the meal. This FAO/WHO method weights each food's GI by its proportional carbohydrate contribution.
What is the difference between glycemic index and glycemic load?
GI measures how quickly a food raises blood glucose per serving containing 50 g of available carbohydrate. Glycemic load (GL) also accounts for portion size: GL = GI * available carbs (g) / 100. A watermelon has a high GI but low GL because a typical serving contains few carbs.
Where can I find GI values for foods?
The University of Sydney maintains the International GI database, which is the most comprehensive peer-reviewed source. The USDA and FAO have also published GI data. GI values can vary by cooking method, ripeness, and food variety.
Do fats and proteins in a meal affect the GI?
Yes. Fat and protein in a mixed meal slow gastric emptying and reduce the glycemic response, so the actual blood glucose rise from a mixed meal is typically lower than the calculated weighted GI suggests. The weighted GI is a planning tool, not a precise prediction.
Official sources
- FAO/WHO: Carbohydrates in Human Nutrition (FAO Food and Nutrition Paper 66).
- USDA FoodData Central: FoodData Central.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.