I'm not sure I get why people are dividing your round trip miles by 2, unless you're climbing a hill one way and descending the other, you're probably doing some of the climbing each way. Obviously, the average grade of a round trip is zero because you end up at the same altitude, but that's a truly useless statistic. Because of the geography where I ride, I do a lot of round trip rides that involve climbing and descending a big hill in both directions of a round trip. Since I'm really only interested in the climbing effort, my solution for this is to treat the descents as 0% grade rather than negative. Descent doesn't negate my climbing efforts.

Here's a handy calculator: https://www.omnicalculator.com/const...levation-grade

You can change the horizontal difference to miles, km, whatever.

BTW, my belief is that the longer the distance, the less useful the average grade is as a statistic. What you're doing is obviously a lot of climbing, but I find how the climb is distributed on a route to be a bigger determinate of how tired I'm going to get than the total amount of climbing. For example, if I have a 15 mile ride with an average 2.5% grade, it's going to be a lot harder if 14 miles of that ride are essentially flat than if it's a consistent 2.5% per mile.

You're doing great! Is that on roads or dirt?