55
30
g
16.5
16.5
1
2
55
30
g
16.5
16.5
1
2
The Glycemic Index (GI) Calculator helps you evaluate the blood sugar impact of foods by calculating both the Glycemic Index and the Glycemic Load (GL). While GI tells you how quickly a food raises blood sugar, GL tells you how much it raises blood sugar by accounting for portion size — providing a more complete picture for dietary planning, especially for people with diabetes or those seeking to manage their weight.
The Glycemic Index was developed in 1981 by Dr. David Jenkins at the University of Toronto. It ranks carbohydrate-containing foods on a scale of 0-100 based on how rapidly they raise blood glucose compared to a reference food (pure glucose = 100). Foods are classified as Low GI (≤55), Medium GI (56-69), or High GI (≥70). Low GI foods produce a slow, gradual rise in blood sugar, while high GI foods cause a rapid spike.
However, the GI alone can be misleading. Watermelon, for example, has a high GI of 76 but only 6g of carbs per serving — a small portion causes minimal glucose response. This is where Glycemic Load becomes essential. GL = GI × Carbohydrate Content / 100, and is classified as Low (≤10), Medium (11-19), or High (≥20). Watermelon's GL per serving is only about 5 — low — despite its high GI.
For diabetes management, GL is generally more useful than GI because it reflects the actual glucose impact of the food as eaten. A food with a high GI but low carb content per serving may be perfectly acceptable, while a food with moderate GI but large carb portions can significantly raise blood sugar. This calculator combines both metrics to give you a comprehensive assessment.
GI values can be referenced to either glucose (the international standard, GI = 100) or white bread (GI = 100 on bread scale, ~70 on glucose scale). This calculator allows you to input values on either scale and automatically converts to the glucose reference for standardized results. GI databases from the University of Sydney and the International GI Tables provide values for thousands of foods.
The calculator uses the following formulas:
Glycemic Load = GI × Total Carbohydrates (g) / 100
Total Carbs = Carbs per Serving × Number of Servings
If the GI is entered on the white bread scale (GIbread = 100), it is converted to the glucose scale: GIglucose = GIbread × 100 / 70
GI Categories (glucose scale): Low ≤55, Medium 56-69, High ≥70
GL Categories: Low ≤10, Medium 11-19, High ≥20
GI Category 1 (Low ≤55): The food causes a slow, gradual rise in blood sugar. Good choices for diabetes management and sustained energy. Examples: oats, legumes, most fruits, sweet potatoes. GI Category 2 (Medium 56-69): Moderate blood sugar impact. Acceptable in moderation. Examples: basmati rice, whole wheat bread. GI Category 3 (High ≥70): Causes rapid blood sugar spike. Limit in diabetic diets. Examples: white bread, white rice, potatoes. For GL: Low (≤10) means minimal glucose response, Medium (11-19) is moderate, High (≥20) indicates significant glucose impact per serving.
Inputs
Results
Rolled oats: GI 55 (low), 27g carbs per serving, GL 14.9 (medium). Good choice for sustained energy.
Inputs
Results
White rice: GI 73 (high), 90g carbs (2 servings), GL 65.7 (very high). Significant blood sugar impact.
The Glycemic Index (GI) ranks carbohydrate foods on a scale of 0-100 based on how quickly they raise blood glucose. It was developed by Dr. David Jenkins in 1981. Low GI foods (≤55) cause gradual rises, while high GI foods (≥70) cause rapid spikes. Pure glucose is the reference at GI = 100.
Glycemic Load (GL) = GI × Carbohydrate content per serving / 100. It accounts for both the speed (GI) and amount of glucose impact. A food can have a high GI but low GL if the carb content per serving is small (e.g., watermelon: GI 76, GL 5).
GL is generally more useful because it reflects the actual glucose impact of a real-world portion. A diabetic can eat small amounts of high-GI foods without major glucose spikes. However, both metrics together provide the most complete picture for dietary planning.
Processing (more processed = higher GI), cooking method (al dente pasta has lower GI than overcooked), ripeness (riper fruit has higher GI), fiber content (more fiber = lower GI), fat and protein content (slow gastric emptying = lower GI), and starch type (amylose vs amylopectin).
No. GI values are averages from standardized testing (usually 10+ subjects). Individual glycemic responses vary by up to 25% based on gut microbiome, insulin sensitivity, physical activity, stress, and other factors. Use GI as a general guide, not a precise predictor.
Legumes (lentils, chickpeas: GI 25-35), most fruits (apples, berries: GI 30-40), oats, barley, sweet potatoes, nuts, yogurt, and whole intact grains. Pairing high-GI foods with protein, fat, or fiber lowers the overall glycemic response of the meal.
Yes — the same food can have different GI numbers depending on the reference scale. On the glucose scale: low ≤55, high ≥70. On the bread scale: low ≤40, high ≥50. Always check which scale a GI value uses. This calculator standardizes to the glucose scale.
Research suggests low-GI diets may help with weight management by promoting satiety, reducing insulin spikes (which promote fat storage), and providing sustained energy. However, total calorie intake remains the primary factor for weight loss. GI is one tool among many.
Yes. While carb counting is the primary dosing tool for type 1 diabetes, the GI of foods affects how quickly blood sugar rises after a meal, which influences insulin timing. Low-GI meals may be easier to match with insulin, while high-GI meals may require earlier bolusing.
Yes, significantly. Cooking gelatinizes starch, increasing GI. Al dente pasta (GI ~45) has a lower GI than overcooked pasta (GI ~60). Cooling cooked starch increases resistant starch and lowers GI — cold potato salad has a lower GI than hot mashed potatoes.
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