What this calculator does
Glycemic index ranks carbohydrate by how fast it raises blood glucose, but it says nothing about how much carbohydrate a serving contains. Glycemic load fixes that by multiplying the two together.
The correction can reverse a judgement. A food with a modest index of 55 in a 50 g serving gives a load of 27.5, in the high band, while one with a high index of 75 in a 30 g serving gives 22.5. The second food raises glucose faster per gram, and the first delivers more of it.
The formula
Multiply the glycemic index by the grams of carbohydrate in the serving and divide by 100. The result is read against bands of 10 and below for low, 11 to 19 for medium and 20 and above for high.
| Term | Meaning |
|---|---|
| Glycemic index | How fast a carbohydrate raises blood glucose, on a 0 to 100 scale against glucose itself. |
| Glycemic load | Index multiplied by the carbohydrate in the actual serving. |
| Serving size | The variable the index ignores and the load accounts for. |
The inputs explained
| Field | What to enter |
|---|---|
| Glycemic index (0-100 scale) | The glycemic index of the food, on the 0 to 100 scale. |
| Carbohydrate per serving (g) | Grams of carbohydrate in the serving you are actually eating. |
When to use it
Comparing two foods fairly
A high-index food in a small portion can carry less load than a low-index food in a large one.
Planning a meal
Load is additive across a meal in a way index is not.
Understanding why watermelon is not a problem
A high index on a food that is mostly water produces a low load.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How does the glycemic index change the load?
Four glycemic index values at the same serving size.
| Glycemic index (50 g serving) | Glycemic load | Category |
|---|---|---|
| GI 40 | 20.0 | High |
| GI 55 | 27.5 | High |
| GI 75 | 37.5 | High |
| GI 95 | 47.5 | High |
Questions
Which matters more, index or load?
Load, for most practical purposes, because it accounts for what you actually eat. Index is still useful for comparing foods gram for gram, but a ranking that ignores portion size can mislead badly.
How accurate are published index values?
They vary considerably. Index is measured in small groups of people and differs with ripeness, processing, cooking method and what else is eaten alongside. Published figures are averages with meaningful spread around them.
Does this apply to a whole meal?
Loads are roughly additive, so summing across a meal gives a usable estimate. Fat and protein slow absorption, though, so a mixed meal generally behaves better than its carbohydrate content alone suggests.
Should I manage diabetes with this?
Not on your own. Glycemic load is one tool among several, and dietary management of diabetes should be planned with a doctor or dietitian who knows your treatment and your readings.
For carbohydrate after fibre is deducted, see the net carbs calculator. For average glucose from A1C, see the estimated average glucose calculator.