I have not used a bolus calculator, but my insulin pump will give me a recommended bolus for meals and snacks when I input my BG level and the number of carbs I will be eating. My BG level is determined from my glucose meter, and there are discrepancies there. If the meter gives me a number that is 20 or more points higher/lower than my true BG, then the amount of insulin I use is more/less than I need. This results in my post meal BG being high or low. It can even lead to hypoglycemia. The lack of meter accuracy is the problem here. It does not usually happen, but it does at least once each day. If I test my BG twice before taking my insulin, I can see numbers that are significantly different. If meters were more accurate, and consistent, my BG after meals would be more stable. Inaccuracy with glucose meters can be a major problem.
I am very much concerned about the artificial pancreas (AP) that will be available in the future. I have read that the Dexcom CGM will determine the BG level, and based on that, glucagon or insulin will be administered to correct high and low BG numbers. Many online friends are saying that the Dexcom numbers are sometimes faulty. The amount of glucagon for a low Dexcom number, or the amount of insulin for a high Dexcom number, could result in hyperglycemia, or hypoglycemia, accordingly. I will not be using the AP for that reason. Inaccuracy with glucose meters and CGMs can be a major problem. I hope that the accuracy will eventually improve so that these problems will be minimized.