I also recommend the MyFitnessPal app - it's a shame it doesn't seem to allow BG tests to be recorded (unless someone knows how), but I've found it to be accurate and less fiddly than spreadsheets - I was using the Google Sheets app. The barcode scanner is very easy to use. It's also easy to quickly build up "standard meals" if you tend to cook or eat the same meals on a regular basis, so you don't have to input the same ingredients repeatedly.
Interestingly, MyFitnessApp gives you much more data to analyse than carbs - I was particularly keen to see my calorie intake as I keep losing weight (appreciate others may not have this concern, but it can be used as a diet aid) and I also learnt that my diet is deficient in vitamin C, calcium and iron.