How this calculator works
GI is experimentally measured, not derivable from carbohydrate grams alone. Meal mode uses supplied glucose-scale GI values, weighted by available carbohydrate grams. It is a theoretical estimate; directly measured mixed-meal responses can differ. Test mode divides incremental glucose-response areas from comparable tests. A single ratio is not a complete standardized multi-participant GI study. There is no built-in food database. The result is an estimate for information only and is not medical advice.
Formula
Meal GI = sum(GI_i x carbohydrate_i)/sum(carbohydrate_i). Calculated meal GL = sum(GI_i x carbohydrate_i)/100. Response ratio GI = 100 x test-food incremental AUC/mean glucose-reference incremental AUC.
Worked example
A meal with 30 g carbohydrate at GI 40 and 10 g at GI 80 has GI (1200 + 800)/40 = 50 and calculated GL 20. Test and reference areas of 75 and 100 give a ratio of 75.
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Frequently asked questions
Where do I get the GI values?
Use measured values for the actual food, preparation and glucose-reference scale. Labels and recipes alone cannot establish GI.
Should I use total or available carbohydrate?
Use the available carbohydrate convention of the GI source. Do not mix values based on incompatible fibre or sugar-alcohol conventions.
Does this predict my glucose reading?
No. Meal composition, preparation and individual physiology affect the response. It does not recommend a medication dose.