Glycemic Load = (Glycemic Index X (g) Carbs/serving)/100
Thus, for most people, the glycemic load is a more meaningful measure of the glycemic impact of different foods. Considering the two examples from the glycemic index section, their glycemic loads would be:
(89-127 X 11 g Carbs/Serving)/100= 10-14
(103 X 6 g Carbs/Serving)/100 = 6.18
As a general guideline for glycemic loads of foods : 20 or above is high, 11-19 is medium, and 10 or below is low1,2.
Putting it all together, popcorn and watermelon have high glycemic indexes, but medium and low glycemic loads, respectively.
You can also use the top two links below to find the glycemic loads of foods. However, please note that in the second link the glycemic loads are calculated using 100g serving sizes for all foods. This might not be the actual serving size for all foods, which is what is typically used, so it is important to keep this in mind. The third link is to the NutritionData estimated glycemic load tool that is pretty good at estimating the glycemic loads of foods, even if actual glycemic indexes have not been measured.
References & Links
Glycemicindex.com – http://www.glycemicindex.com/
Glycemic Index & Glycemic Load of Foods – http://dietgrail.com/gid/
Estimated Glycemic Load – http://www.nutritiondata.com/help/estimated-glycemic-load