Glycemic load calculator for a meal or a recipe

What glycemic load actually measures

The glycemic index answers a narrow question: if you ate exactly 50 grams of available carbohydrate from this one food, how far would your blood sugar rise over two hours compared with 50 grams of glucose? It is a property of the food, tested in a laboratory to a published protocol (ISO 26642:2010), and it says nothing about your dinner.

Glycemic load closes that gap. It scales the index by how much carbohydrate is actually on your plate. Watermelon has a high glycemic index and a low glycemic load, because a slice of watermelon is mostly water. A modest bowl of rice has a middling index and a high load, because there is a lot of starch in it. If you have ever wondered why the GI tables never seemed to match your experience, that is the reason: you eat portions, not 50-gram carbohydrate equivalents.

This calculator works in load from the start. You add foods and grams, and it sums the load of every item. There is a longer explanation of the difference between index and load if you want it, and a piece on how load relates to the size of a glucose spike.

How the calculation works, with the formula

For each food, the calculator takes the available carbohydrate — total carbohydrate minus fibre — for the weight you entered, multiplies it by that food's glycemic index, and divides by 100. The results are added. If you set a servings number, the total is divided by it, which is how you get the load per portion of a recipe rather than of the whole pot.

The weighted glycemic index shown alongside the result is the index the meal behaves like as a whole: the load of the meal divided by its available carbohydrate, times 100. It is the number to compare against the GI bands, because a single food's GI is meaningless once it is mixed into something else.

Fibre is subtracted because it is not absorbed as glucose. Sugar alcohols, if a label lists them, are not handled here — a packaged product's own label is the better source for those.

Where the food values come from

Every food in the search box is a record in the LOGI food database — the same records behind our food pages and the ones our recipes are built from. Each row in your meal links straight to that food's page, so you can check the carbohydrate, fibre and index we used rather than taking them on trust.

The two sets of bands above the calculator come from different places, and it is worth knowing which is which. The glycemic index bands are the University of Sydney's — the group that runs the testing service and compiles the international GI tables with Atkinson, Foster-Powell and Brand-Miller. The glycemic load bands are not: Sydney publishes the GL formula but no GL cut-offs, and the familiar low, medium and high figures come from Brand-Miller's own work as set out by the Harvard T.H. Chan School of Public Health. Both sources are named under the scales.

When glycemic load does not apply

Glycemic load describes carbohydrate. It says nothing useful about a meal that has almost none, and a plate of grilled fish and greens will read near zero without that being a health verdict.

It also cannot see the things that change the same meal's effect on the same person: how much fat and protein is on the plate, whether the food is liquid, how processed it is, what order you eat it in, whether you walked afterwards, how well you slept, and where you are in your cycle. Published GI values are averages across a test group, and individual responses to the same food vary widely — two people can eat the same bread and produce different curves.

Treat the number as a way to compare two versions of the same meal, not as a prediction of your glucose. If you want the prediction, that needs your own data.

Using it for a whole recipe

Set the servings field to the number of portions the recipe makes and add every ingredient in the weights the recipe calls for. The result is the glycemic load per serving, which is the number worth knowing — a stew with a load of 60 is not alarming if it feeds five.

The quickest way to lower it is usually not to remove a food but to change one: a lower-index starch, more of the vegetables that are already in there, or a little more fat or protein alongside. Our quick guide to low, medium and high GI foods is a reasonable place to look for the swap.