I had the same concern until I found a tool that makes it really easy. I use the USDC Calculator on Paybis and you can find it right there. It lets you convert USDC to USD or any other currency with real time rates, and it also has a profit calculator where you can enter a past date and see how your investment would have performed. It shows a 7 day price history as well, which is useful for spotting any temporary deviations from the peg. The interface is clean and straightforward, no ads or clutter. It has become my go to for both quick conversions and checking historical performance. If you want to keep an eye on your stablecoins without the guesswork, this is a great tool to use.