“It's not that long of a hike.”
You and a friend are in the countryside. You want to hike to the top of a small mountain, but your friend isn't sure if he wants to do it. You say this to convince him to hike up there with you.
It's not that long of a hike.
Use "not that ___ of a ___" when you want to:
- describe what something is not ("long")
- tell what category it's in ("a hike")
She's not that good of a singer.
This isn't that old of a building.
It really isn't that big of a deal.
Of course, you could also say:
It's not a very long hike.
She's not a very good singer.
But these versions put more emphasis on the description ("long", "good"), while "not that ___ of a ___" puts a little more emphasis on the category.
"Hiking" means walking over rough ground, like in the mountains, in a desert, through a forest, etc. People usually hike for fun.
"A hike" means one complete session of hiking. This can last for a few minutes or for several days:
We did a ten-day hike along the Appalachian trail last summer. It was gorgeous.