Glycemic Index Calculator

GI ranks how fast a food's carbohydrate raises blood sugar, on a 0-100 scale relative to pure glucose -- but it ignores portion size. GL fixes that by scaling GI to the actual carbohydrate in your serving: GL = GI x carbs per 100g x serving size / 10,000. Watermelon is the classic example of why both matter -- it has a high GI (72) but very little carbohydrate per serving, so its glycemic load is low. GI alone would flag it as a food to avoid; GL shows it usually isn't a big deal in a normal portion.

GI: 0-55 is Low, 56-69 is Medium, 70 and above is High. GL: 0-10 is Low, 11-19 is Medium, 20 and above is High. These are two separate scales measuring different things, so a food can land in different bands on each -- high GI but low GL (watermelon), or occasionally the reverse with a large low-GI carb portion.

Treat them as representative, not exact. The values come from the International Tables of Glycemic Index, where each food is measured by feeding a fixed carbohydrate portion to volunteers and tracking their blood glucose response. Ripeness, cooking method, and variety can each shift a food's real GI by 10-20 points or more -- well-cooked pasta has a higher GI than al dente, for instance, and a green banana differs from a ripe one.

Yes -- this is real physiology, not just a rule of thumb. Adding protein, fat, or fibre slows gastric emptying and blunts the glucose response of the meal as a whole. It's also why a single food's GI value is most directly useful for something eaten close to alone, like a slice of bread, and less directly applicable once it's part of a mixed plate -- GI values are measured for individual foods, not combinations.

It's a reasonable planning tool for general blood sugar awareness, but it's not a substitute for individualized medical nutrition therapy, and individual glucose responses to identical foods vary more than the GI table alone captures. For diabetes specifically, GI/GL concepts are commonly used alongside carbohydrate counting, but insulin dosing and specific dietary targets should follow your clinician's guidance rather than this calculator.