Glycemic Load Calculator

Glycemic Index (GI) ranks a food based on the blood-glucose response to a fixed amount of available carbohydrate. Glycemic Load (GL) scales that value to the available carbohydrate in your serving: GL = (GI x available carbs per serving) / 100. This makes GL sensitive to portion size.

The widely cited Harvard School of Public Health cutoffs are: low GL is 10 or less per serving, medium is 11 to 19, and high is 20 or more. For a daily total, under 100 is considered low and over 120 is considered high. This calculator labels both your per-serving GL and your total GL (per serving x servings) against the same bands.

Watermelon has a glycemic index of about 76, which is firmly in the high band, but a typical 1 cup serving only contains around 11 g of carbohydrate because it is mostly water. The GL math (76 x 11 / 100 = 8.4) lands well under the low cutoff of 10. This is the classic example of why GL is more useful than GI alone: a fast-rising food in small carb amounts still produces a small blood glucose response.

For people with type 2 diabetes or prediabetes, lower total daily GL is associated with better post-meal blood glucose and lower A1C over time. Targeting low-GL servings most of the time, then pairing higher-GL foods with protein, fat, or fiber to slow absorption, keeps spikes flatter than carb counts alone would predict. GL does not replace carb counting for people on insulin, but it adds a useful quality signal on top of it.

Total carbs treat 30 g from white bread the same as 30 g from lentils, but the bread spikes blood glucose far higher and faster. GL captures that quality difference by weighting carbs by their glycemic effect. Two foods with identical carb counts can have GL values that differ by a factor of three or more, which translates into very different blood glucose curves, satiety, and energy crashes.