The OP only ask about a 1/4 mile of climbing compared to 2 miles or more of climbing. Not sure how we got to the mountains so fast where 14 to 30 miles of fairly constant climbing might be involved.
As more to the OP's question, I think it mainly just comes down to past experience of what you have ridden before and your best guess. Augmenting your past experience with route profiles to see the grade of the sections of what you did and what you wish to do help in making that comparison. As does knowing what the surface is like. And for most paved road google maps can give you a street view which you can "drive" to see what the pavement is like and the surroundings. However those sometimes are years old may not be exactly the conditions today.
RideWithGPS, Strava, GarminConnect, MapMyRide and other websites can show you route profiles and the grade percent for any segment you select out of that route profile.