Ok, here is a view by age. The bars represent their age when (if!) they become president and shows the full 8 years of their term.
There are basically 3 groups here – the first are the kids, in their late 30s/early 40s, they would be younger than JFK by 4-5 years if they win to become the youngest US president by far. The mid-tier, from their mid-50s to late 60s makes up the bulk of the bunch. Finally, the oldies will be in their late 70s or older when they start. Elizabeth Warren would be the oldest president ever if she went 2 terms and Bernie would be the oldest president ever on day 1!
Frankly, I didn’t realize that Trump was older when Reagan when they started, so if he serves 2 terms, he will be the oldest president we have ever had.