In my base running phase for crosscountry all of my mile times have been sub 7:00, averaging 6:20 pace ..?

Question

in decent comfort, can I expect sub 15 minute times in the 5k?

Answer 1

Well I'm going into my 3rd year in high school, and I'm base training just a little faster then you are. My PR is about 15:39. I don't think you can achieve sub 15 at that training. I would suggest sub 16. It could differ since I don't know much about your age, PR, etc.

Answer 2

Note, basing a maximal performance from an easy run  is very inaccurate. It usually works much better to use a race performance to determine your training speeds.

However if 6:20 is truly your easy run pace, i.e. you are not pushing the pace and actually doing a tempo run for your easy runs, you should be running a little over 15 minutes for a 5k on the track or road.  Cross country courses can vary a lot and often they are slower.  My rule of thumb is to add 30 seconds to a track or road time for cross country so my guess is that you're probably more like 15:35 to 15:50 for cross country based on your training speed.

Answer 3

I don't think so but it depends on how much endurance you have.

I run a 4:50 mile time going my fastest. My 5k time is around 18 minutes which isn't that great for me.

If you want to get a 15 minute time for the 5k, I would recommend training yourself to run a five minute mile. After that, train yourself by doing mile repeats at a five minute pace.