Good time 5km run?Watch
Xtra: I only started running last month.
I'd agree with the above, although that is a huge range of course. 20 mins put you in probably one of the best runners in your area, 25 mins is much more common but fair bit above what the average 18 year old could do.
I'm about 2 months into getting into running again and my 5k pace is currently 21 minutes, 10k is 48 minutes though I could probably do ~46 on a better day.
Try to do a combination of running further than 5k on some days and running faster than your previous pace on others. Make sure to do more exercise than just running as this will help too, even if this is just sit-ups, press ups, squats after your run.