Why do GI values differ between sources?

GI is measured by feeding healthy volunteers a portion containing 50 g of available carbs and tracking blood glucose for 2 hours. Differences come from: (1) which reference food (glucose or white bread); (2) ripeness, cooking method, processing; (3) individual variation in test subjects. The University of Sydney database is the most-cited authoritative source.

Does food order matter for GL?

Yes — Shukla et al. (2015 Diabetes Care) showed that eating protein + vegetables BEFORE carbs reduces post-meal glucose by ~37% vs the reverse order. Total GL is unchanged but the timing/amplitude curve flattens substantially.

Are low-GL diets backed by evidence?

Cochrane Review 2017: low-GI/GL diets show modest improvement in HbA1c (~0.2-0.5%) for people with type-2 diabetes. They are not silver bullets, but they are evidence-based and broadly endorsed by ADA, EASD, and WHO dietary guidance.

Salmerón J et al. (1997), "Dietary fiber, glycemic load, and risk of NIDDM", JAMA 277(6); Atkinson FS, Foster-Powell K, Brand-Miller JC (2008), "International tables of glycemic index and glycemic load values", Diabetes Care 31(12); University of Sydney Glycemic Index Database (gisymbol.com); Harvard Health Publishing "Glycemic index and glycemic load for 100+ foods" (2024 update).

Why do GI values differ between sources?

GI is measured by feeding healthy volunteers a portion containing 50 g of available carbs and tracking blood glucose for 2 hours. Differences come from: (1) which reference food (glucose or white bread); (2) ripeness, cooking method, processing; (3) individual variation in test subjects. The University of Sydney database is the most-cited authoritative source.

Does food order matter for GL?

Yes — Shukla et al. (2015 Diabetes Care) showed that eating protein + vegetables BEFORE carbs reduces post-meal glucose by ~37% vs the reverse order. Total GL is unchanged but the timing/amplitude curve flattens substantially.

Are low-GL diets backed by evidence?

Cochrane Review 2017: low-GI/GL diets show modest improvement in HbA1c (~0.2-0.5%) for people with type-2 diabetes. They are not silver bullets, but they are evidence-based and broadly endorsed by ADA, EASD, and WHO dietary guidance.

Salmerón J et al. (1997), "Dietary fiber, glycemic load, and risk of NIDDM", JAMA 277(6); Atkinson FS, Foster-Powell K, Brand-Miller JC (2008), "International tables of glycemic index and glycemic load values", Diabetes Care 31(12); University of Sydney Glycemic Index Database (gisymbol.com); Harvard Health Publishing "Glycemic index and glycemic load for 100+ foods" (2024 update).

Glycemic Load Calculator

GL = (GI × available carbs in serving) ÷ 100 — total daily glycemic load for up to 6 foods. Harvard / Sydney University GI database values.

Inputs

Food 1 — preset

Food 1 — servings

Food 2 — preset

Food 2 — servings

Food 3 — preset

Food 3 — servings

Food 4 — preset

Food 4 — servings

Result

Total glycemic load

33.3

66.0g total available carbs · meal-weighted GI 50 · HIGH per-meal impact (≥ 20)

Slot 1: White bread × 1GI 75, 14.0g carb, GL 10.5
Slot 2: Banana, ripe × 1GI 51, 27.0g carb, GL 13.8
Slot 3: Apple × 1GI 36, 25.0g carb, GL 9.0
— Totals —
Total carbs66.0 g
Meal-weighted GI50.4
Total glycemic load33.27
Per-meal impact bandHIGH per-meal impact (≥ 20)
Daily-total context< 80/day = LOW total daily load
DisclaimerGI/GL values are population averages from University of Sydney + Harvard databases. Individual glycemic response varies (Zeevi et al. 2015 Cell). Not medical advice.

Step-by-step

GL formula (Salmerón et al. 1997, JAMA): GL = (GI × available carbs grams in serving) / 100.
Slot 1: GL = (GI 75 × 14.0g carbs) / 100 = 10.50.
Slot 2: GL = (GI 51 × 27.0g carbs) / 100 = 13.77.
Slot 3: GL = (GI 36 × 25.0g carbs) / 100 = 9.00.
Total GL = Σ slots = 33.27.

How to use this calculator

Pick up to 4 foods from the dropdowns.
Set servings (a "serving" matches the parenthetical size in each option label — e.g. 1 slice of bread, 1 cup of rice).
For foods not in the list, you can't enter custom — for that, the formula is straightforward: GL = (GI × carbs in grams) / 100.
Compare meal GL to the < 10 / 10-19 / ≥ 20 per-meal bands.

About this calculator

Glycemic Load (GL) was introduced by Salmerón et al. (1997 JAMA) to fix a problem with the original Glycemic Index (GI): GI tells you the rate at which a food's carbs raise blood glucose, but it doesn't tell you how much carb is in a normal portion. Carrots have a moderate GI (~35) but only 11 g of carbs per cup — their glycemic load is tiny (3.9). White bread has GI 75 and 14 g per slice — GL = 10.5 per slice, dwarfing the carrot impact. The formula is GL = (GI × available carbs in grams in serving) ÷ 100. Per-meal bands from Atkinson et al. (2008 Diabetes Care): < 10 low impact; 10-19 medium; ≥ 20 high. Daily totals from Harvard Health Publishing: < 80 low; 80-120 medium; > 120 high (associated with type-2 diabetes risk in long-term cohort studies). This calculator pulls reference values from the University of Sydney Glycemic Index Database (gisymbol.com) and Harvard's 2024 published table. Individual responses to identical foods can vary by 3-4× (Zeevi et al. 2015 Cell), so these are population averages, not personal predictions.

Frequently asked

GL is generally more clinically meaningful because it accounts for serving size. Watermelon has a high GI (~72) but very little carb per serving — its GL is only about 5. White bread has similar GI but 3× the GL per slice. Both metrics are used together in modern dietary guidance.