Last updated: 2026-06-22

Glycemic Load

Glycemic load is a measure that estimates how much a serving of food is expected to raise blood glucose. It combines the quality of a food's carbohydrate, expressed as its glycemic index, with the quantity of carbohydrate actually eaten. This calculator returns the glycemic load of a serving and places it in a low, medium, or high band. It is useful for anyone comparing carbohydrate foods, including people managing blood-glucose levels and those planning lower-glycemic meals.

Quality and quantity

The glycemic index (GI) ranks a carbohydrate food on a 0–100 scale according to how quickly and how far it raises blood glucose compared with pure glucose, which is set at 100. By itself the index ignores portion size, so a food can have a high index yet contribute little carbohydrate in a normal serving. Glycemic load corrects for this by scaling the index by the grams of available carbohydrate, which is the digestible carbohydrate that excludes fiber.

The formula

$\mathrm{GL} = \dfrac{\mathrm{GI} \times C}{100}$

Here $\mathrm{GI}$ is the glycemic index of the food and $C$ is the grams of available carbohydrate in the serving. Dividing by 100 rescales the index, which is itself a percentage relative to glucose, into a load expressed per serving.

Worked example

Consider a serving of food with a glycemic index of 64 containing 37 grams of available carbohydrate:

A glycemic load of about 23.7 falls in the high band, driven both by a moderately high index and a substantial carbohydrate portion. Halving the portion to roughly 18 grams would bring the load to about 11.5, into the medium band, illustrating how portion size moves the result.

Interpretation

For a single food or serving, the conventional bands are a glycemic load of 10 or below for low, 11 to 19 for medium, and 20 or above for high. These thresholds describe one item rather than a whole day. A common pattern is that foods with a high glycemic index can still have a low load when the portion is small or watery; watermelon is a frequently cited example because it is mostly water.

Limits

Published glycemic index figures are population averages measured under standardized conditions. Real values shift with ripeness, cooking method, degree of processing, and the protein, fat, and fiber eaten alongside the carbohydrate, all of which slow absorption. Individual blood-glucose responses also vary from person to person and day to day. Glycemic load is therefore best treated as a tool for comparing foods rather than a precise forecast for any one meal. For a related view of carbohydrate quality, see the Added Sugar Limit Calculator.