Tony S. wrote:

Tried using Fitday.com, but it didn't find even my common breakfast
foods in it's database, and it doesn't seem to have a way to enter
sufficient information in the custom foods to support a true net carbs
calculation: it lets you enter Total carbs and Fiber only, not sugar
alcohols or net carbs given on low carb specific products, which I eat
occasionally.

Different people calculate net carbs differently so the word "true" for
a net carb count is a misnomer. I experimented on myself and concluded
that my body absorbs sugar alcohol as carb grams so I count them fully.
I also distrust net carb claims on some labels and I consider their
claims carefully before accepting them. In the end I decided that the
only deduction I'm willing to take is for fiber.

This is part of the deal with fitday being a generalist tool not
specific to low carb. I think you want one that is specific to low carb
and one that has decided to calculate net carb grams based on your
decisions about how to do that. I don't know of such a tool off the top
of my head.