Is 20 to 30 Training Miles Enough to Run a Half Marathon

by Terese
(Ogden, Utah. USA)

I have been a committed runner for a year and a half now and have completed two half marathons with over a dozen 10k races! I have been keeping running on the down-low for a bit, averaging 20 to 30 miles per week.. and I am only just coming out of this quiet period.... and I have signed up for a half marathon in three weeks in California!

Do you think my weekly average right now will be enough to get me through the half marathon well? I am pretty confident I will do ok but not sure that I am putting in enough miles per week like I normally do. Six months ago I was averaging 50 miles per week!!

Answer by Dominique:

Hey there,
Congratulations on that amazing running track record over the past year and a half. Great to see that you have done so many races, great to see you have been able to do 50 mile weeks and that a quiet period is 20 to 30 miles per week.

You are doing well!

Now, to your concern about whether or not 20 to 30 miles per week is enough to prepare yourself for an upcoming half marathon, let's tackle this as follows:

1. Understanding your Training and History
2. Adjust your half marathon goal
3. So, how fast to go?

Understanding Your Training

Now, generally I would say: "Yes, 20-30 miles is sufficient to finish a half marathon.".

But, then it got me thinking... how are you dividing up those 20 miles?

Are you doing 5 x 4 miles each? Or 2 x 5 miles + 1 x 10 miles? Both ways you get to 20 miles.

But, I'd back the runner who is doing the 10 mile long runs over the runner who is doing a maximal long run of 4 miles only!

So, you haven't given me that detail, but as long as you have got a long run in your schedule that is 8-10 miles in length, I think you are going to be fine.

Have your long runs been much shorter in the last three months? Then you might be in for a little bit of a tough day!

Also keep into account that you have done a year and a half of very regular running. You have done 50 mile weeks. When you reduce your mileage, you lose some fitness, but that history counts for something.

With a year and a half of consistent running behind you, I think you are more than able to finish a half marathon.

It may not be your fastest performance. It might even be really difficult towards the end. But, I am sure you can do it based on what you have told me.

Adjust Your Half Marathon Goal

Because your training has been reduced over the past three months or so, one thing I would urge you to do is to adjust your half marathon goal.

Your goal needs to reflect your current fitness. Not the fitness you may have had when you were covering 50 miles per week.

Starting off too fast can be a painful experience in any race. It can be tough in a 5k, but at least a 5k is over before you know it. In the half marathon, starting out too fast, can make the last hour feel like hell.

Believe me, been there done that quite a few times. It can really take the enjoyment out of running the half.

So, How Fast to Go?

It's always a bit tricky to know exactly what you are capable of when preparing for a race. I have listed a few alternatives that could help you work out how fast you can go in your half:

Goal Pace
Firstly, It would not be a bad idea to test yourself with a goal pace workout.

Training Paces
Secondly, if you have a reasonably good understanding of your training paces, you could use the Running Pace Calculator to approximate your race time.

Recent Race
Thirdly, and arguably one of the better predictors, if you have very recently done one of those 10k races, you could use that to estimate your performance in the half using my Race Conversion Calculator.

It is a bit tricky, because a half marathon relies on a strong endurance and with the lower mileage you will have lost a bit of that. The calculators may be a little bit too positive about your future half marathon performance, so keep that into account!

Well done on your running journey so far. Finishing the half marathon in three weeks' time should not be a massive issue. Just be mindful to treat it a little bit conservatively. Going out too fast will take some of the joy out of the second half of the race. Best of luck with the remainder of your half marathon prep. Enjoy and I hope you keep on enjoying running and racing as much as you have been doing in the past couple of years!

Kind regards,
Dominique