Depending exactly on the brand you would be looking at about 15 "net" carbs in 3 cups (about 19 gross carbs with 4 grams of fiber making it a "high fiber food").

Popped in oil would not add carbs but would add fat over air popped if you are watching calories.

15 net carbs is often cited as the required number of carbs to stop your system from going back into fasting mode, so shouldn't raise you too high but it is not "insignificant".

For perspective, one and a half medium sized oranges would contain the same 15'ish net carbs or you could put 4 teaspoons of table sugar in your coffee or tea and get the same "carb load" as the 3 cups of popcorn.

What l have read that popcorn is not a diabetics friend so if you won't popcorn you should have it as a treat not as a regular daily thing hopefully this helps you out.

butter does NOT raise your blood sugar. It's the corn! You gotta learn fat is not evel you were taught wrong your whole life forget it.

I eat Skinny Pop plain single bags.

You would have to refer to the nutrition label to know how much a portion is in Net Carbs. Our Carbs tolerance is different for each of us, so you would also have to check your sugar level before and 2 hrs after and see if it spikes it too high above 7.7 (139). I can eat popcorn but like maybe 40 g maximum, instead of the nutrition label on the one we buy stating 1 portion is 46 g (which I have tried and failed). So I weight my popcorn on a kitchen scale instead of measuring in a cup. I can eat corn twist at half what a portion is on the bag, I also eat chips at times but half portion, for both I usually eat 25 g or less and I am OK with both. But that is my tolerance for my diabetes.