On the calculator, you can click the Save tab, then the Save button to generate a URL to bookmark.
Here's your proposed setup:
30-46 front, and 11-36 rear at 70 to 85 rpm -- is that good cadence for your gravel riding?

And see the Speed tab: Try 45 rpm to see the mph for your lowest gear at this lowest "sortof reasonable" cadence: 2.9 mph. It's 3.9 mph at 60 rpm.

Tradeoffs:
the 30 chainring only goes to about 15-17 mph. good enough.
the big chainring has fairly large jumps between shifts in the 15-20 mph range. But that's typical of 11-36 wide range cassettes.

Quite low gearing--good. Low enough? It depends just how steep and rough your gravel roads get.