How do you calculate glycemic load?

GL = (GI × available carbohydrate in grams) ÷ 100. Available carbohydrate is the carbohydrate that is digested and absorbed, usually estimated as total carbohydrate minus fibre.

What counts as a high glycemic load?

Per serving, 10 or below is low, 11 to 19 medium, and 20 or above high. Daily totals are often quoted as under 100 low and over 120 high, but we could not trace those to any authoritative source, so we would not rely on them.

Is glycemic load better than glycemic index?

For deciding what to eat, yes — GI describes the food in a fixed 50 g carbohydrate test dose, while GL describes your actual serving. They answer different questions.

What Is Glycemic Load? The 60-Second Version

Q: What is glycemic load?

Glycemic load is a food's glycemic index multiplied by the grams of available carbohydrate in the serving you actually eat, divided by 100. It scales the index to the portion.

Short answer: glycemic load takes a food’s glycemic index and scales it to the portion in front of you.

GL = (GI × available carbohydrate in grams) ÷ 100

Available carbohydrate is the part that gets digested, absorbed and raises blood glucose. In practice it’s estimated as total carbohydrate minus fibre, though the reference method (ISO 26642) also excludes resistant starch and polyols.

One trap worth knowing if you read EU labels: they already declare available carbohydrate, so subtracting the fibre figure again double-counts it. “Total carb minus fibre” is a US-label operation. More on that in net carbs versus total carbs.

The thresholds

Per serving
Low	10 or less
Medium	11–19
High	20 or more

These per-serving cut-offs are the standard ones, published by Harvard’s Nutrition Source and Oregon State’s Linus Pauling Institute.

You’ll also see daily thresholds quoted, usually “under 100 is low, over 120 is high”. We looked for the source and couldn’t find one: those numbers appear in popular diet writing but not in the University of Sydney’s material, the Linus Pauling monograph, Harvard’s page, or the international GI tables. Treat them as a rule of thumb nobody has stood behind, and use the per-serving figures instead.

Two examples that explain the whole idea

Watermelon. The number everyone quotes is a GI of 72, from 1990s Australian testing. More recent testing runs much lower, and the University of Sydney now gives a mean of 50 across four varieties. Either way, a 120 g wedge holds only about 8.6 g of available carbohydrate, because watermelon is mostly water.

GL = (50 × 8.6) ÷ 100 = 4.3   → low

Even at the old GI of 72 the load only reaches 6. The portion, not the index, is doing the work.

White rice. Published GI ≈ 73. A 150 g cooked serving holds about 40 g available carbohydrate.

GL = (73 × 40) ÷ 100 = 29.2  → high

Nearly the same index as the old watermelon figure, five to seven times the load. The difference isn’t the food’s quality — it’s how much digestible carbohydrate the serving contains. That’s the entire reason GI alone is misleading as a shopping heuristic.

Why GI needs the correction

Glycemic index is measured by feeding volunteers a portion of food containing exactly 50 g of available carbohydrate and tracking their blood glucose against a reference. That fixed test dose is what makes different foods comparable — and it’s also what makes GI a poor description of dinner, where nobody eats to a 50 g carbohydrate target.

GL puts the portion back in. It’s the same measurement, un-normalised.

What it doesn’t tell you

GL is arithmetic on published values, not a prediction of your blood glucose. Individual responses to the same meal vary substantially between people, and a mixed meal — fat, protein, fibre, cooking method, what you ate before it — behaves differently from the food tested alone. Anyone selling GL as a personal spike forecast is overselling it.

Read it as what it is: a portion-aware comparison between options. A tool for noticing that the bowl matters as much as the grain.

Try it on your own numbers

The glycemic load calculator does the multiplication for a serving you choose, and the food-fact posts here run the same math on real plates — rice, oatmeal, pasta.

In 3sense Food it happens per entry: GI arrives published, GL arrives calculated from the grams you logged, and if the underlying value doesn’t exist for that food, the app says not available rather than inventing one.