I think the standard answer here is to plug your 5k time into the mcmillan (or similar) calculator and use those training paces and predictions. During your training, there are some predictor workouts you can do r even run a tune up 10k, which will give you a better idea of where you are in your training. A common half goal is to break 2 hours; let's say you run a 27 min 5k, that predicts a 2:05 half....so I would think somewhere in that 2-2:10 range would be good and you can better plan when you have a newer 5k time.

I think some feel that mcmillan's race predictions are a bit fast though; however, I used one of his plans for my first marathon and was pretty right on. I think I even beat the predicted time for a recent half I ran.

Maybe I'll just make my goal 2:05 for this first time around and try to break 2 hours when I have more training, like the October race that I am planning.

2:05 will be right at a 9:30 minute pace, which is about 45 seconds per mile over your 5k PR. If you keep to your training plan, especially if you're including some speed work once a week or so, that should be a pretty easy goal to hit. I think you'll surprise yourself.

Having a similar 5K pace when I started training and having a similar goal, I made sure I included all the intervals and tempo runs my plan called for and ended my training regiment with a few runs around 14.5-15 miles (pretty sure it was Jeff Galloway speaking at the expo for the Wine and Dine at Disney (I was there to run the half relay) who said "If you just want to finish, just stick to 13 miles on your long runs, if you want to finish strong, you need to run farther." which made sense.). I think I finished it at 1:56 or something like that, blew away my goal.

Anyway, my point is, don't sell yourself short. You're capable of running at a decent clip now. I think you'll find, especially if you stick to the plan, you'll hit that goal easier than you think.

There are lots of variables to running a HM compared to a 5K (having run 5k, HM and full marathons). It is more than just trying to run a 5k race that is 4.22 times longer.

There are calculators that can help but they also assume some level of training for that distance. McMillan and Galloway both have good calculators that give comparable results. They also assume that there is a level of training to take you to that distance. Galloway's calculator (assuming a 27 minute 5k) would predict that you could do a 2:08 and change.

But there are many factors that go into that. I ran a 25:32 5k earlier this year and could have run it a little faster and maybe closed in on 25 minutes. But that speed did not translate into a sub-2:00 half-marathon. At the time I ran the HM in 2:13.

Granted, my HM pace was faster than the pace that I ran in two previous full marathons (when I crossed the halfway point timer), but there is a different running strategy for the full compared to the half. When you cross the finish line in the HM, you're done. When you cross the timer at mile 13.1 you are only halfway done and have a whole HM yet to run. Now, I run the 5K for fun and a quick check on speed but I find my time more variable than the mid-full distances. I think Fitzgerald might be on to something around the whole fueling/race weight issue.

BTW, since I ran that first HM (after running two full marathons), my time has gotten progressively faster in the HM (just ran a hilly course in 2:01 PR). These recent races have been part of my training schedule for a full-marathon and have landed on weekends dedicated to speed runs for the full. Since there is a longer term goal, this means that I have run at a pace consistent with speed work and then recovery for the upcoming weeks. I run a very flat course in Myrtle Beach in a couple of weeks and if everything lines up, a sub-2:00 may be possible. Both my most recent mile timed run and a recent 5k race on a hilly course predict a sub-2:00 HM. It is still just a training run (my last full speed workout) for the full marathon I am running in early November.

If I were to put a range on your times (in April), I would say 2:05 -2:15 is reasonable.

One other thing, when I ran the Rock n Roll Raleigh full marathon in April, it had gone from being cold-cool during the late winter / early spring training period to suddenly warming up. Welcome to April in North Carolina. It was "brutal" according to a number of people who ran the half and full and didn't adequately take the sudden temperature rise (and no time to acclimate) into account. By contrast, I did not think it "brutal."

I did and made some really smart decisions about running pace in that weather by adjusting my pace to be slower from the very start and knowing that there was a lot of exposed (little shade) roadway and hills on the way back in to the finish. I set a PR and came away from that race with a smile and ready to go onto my next race. By comparison, a coworker who had run marathons at a much faster pace than I was capable (at the time), ran one of his slowest marathons and dragged himself across the finish only six-minutes in front of me. The weather was a real wildcard at that time of year and the combination of the temperature and the course took its toll on people.

Two people died in the HM that day (they were runners and it was never revealed whether there was some underlying condition that had remained hidden for these two guys). One collapsed at the finish and the other died at Mile 11. No such occurrence amongst the full marathoners. We all sign those waivers and if we've trained well, the chances are that we'll make it through just fine. But in the absence of other information to the contrary, the running community around here thinks that they just didn't factor in the sudden temperature rise and were running too hard for conditions (both hilly and warm).

Just keep the environmental factors in mind as you come to race day. You'll know how your training has gone and will be able to make a more informed choice as you get closer to the date.

The last poster reminded me of what John "the Penguin" Bingham has said in his books with regard to these races..."always finish the race the same day that you started it!" He tells his interesting story about how not to train and how he started a race and didn't finish it until a year later.

April of next year? I think you should assess your fitness a little before the actual race. Right now with your 5k times and mileage, I'm thinking 2:15ish is more realistic. But, as you continue with your mileage base, train, and gain fitness, you'll get a better feel for your time next year. Do a longer race before your half - a 10k or 15k would be a better measure.

Simply for illustration purposes: I haven't raced a 5k since May of 2011 but at that time, my time was 25:55. I then did a 10k @59 minutes and a 15k in 1:39. This all translated to a 2:08 first half marathon. I think my mileage at that time was similar to yours.

Fast forward to May of 2012: that's when I got it down to 2:00 and my 10k also went down to about 53 minutes. I think the 10k was a better guage. That year I got it under 2 hours but again, I gauged this effort from my 10k times. Plus adding mileage.

Your rate of improvement may differ greatly from others, so see where you are in March or so.


Good luck!