Results from calculations in some proprietary flavours of bc have up to 99 decimal digits before and after the decimal point. This limit has been greatly surpassed in GNU bc. I don't know what that limit is, but it's at least many, many tens of thousands. Certainly it's more than any GUI-based calculators (I've used) could accomodate.

Pretty much every linux distribution ever ships bc. It's a pretty small/light console based calculator. It's actually quite powerful and simple to use. I found a good article that explains how to use it for your everyday math.