If you've ever hit the wall in a marathon you'll know that pacing is vital. But how do you know what pace you should be running at? Start out too fast and you'll blow up in the final third of the marathon. Start out too slow and you won't reach your marathon goal. So how do you calculate your marathon pace?

In this video, Lindsey shares with Brad a simple rule of thumb that you can use to prevent yourself from starting out too fast and blowing your chances of achieving your marathon goal.

Brad Brown: Welcome onto this edition of Run with Coach Parry, I’m Brad Brown; we’ve got the coach with us once again. Lindsey Parry, howzit?

Lindsey Parry: Very good Brad, awesome to chat again, how are you doing?

BB: Very, very good and definitely great to chat again. We are in the midst where it’s a new year and everyone is fired up and running and there’s lots of marathon training going on, which I quite like. Today’s question popped up in the forum, on the Coach Parry online training platform and I think it’s a great one. This member was asking: How do you determine what your race pace is for a marathon? I think it’s a great question and I think one that not enough people are asking.

How to calculate your marathon pace

LP: Look, I’m going to give a very basic, almost rule of thumb way to do it. Typically if I’m going to calculate it, I do use a 5km and a 10km and a half marathon time to try and determine if you’re improving as you’re going longer or if you’re getting better as you’re going longer and then we can do some slight tweaks.

Essentially, if you’re running 5km races fairly hard or you’ve got some decent 5km times, I reckon from a 5km to a 10km, you can be between five, if you’re very, very conditioned and eight or nine seconds per km slower, you’ll be able to hold for a 10km.

Then you will be in the region of eight to 12-13 seconds per km slower when you then move from that 10km to the 21km and then from the 21km to the marathon, you’re probably also looking around 8-10 in a very conditioned person or somebody who gets relatively better as time goes by, you’re probably looking at about eight seconds per km slower, up to around 15 seconds per km.

Your fitness levels dictate your pacing strategy for a marathon

Obviously, if you’re someone who struggles and gets slower as you go longer, then you’re probably looking at more along the lines of 16-17-18 seconds per km. That’s kind of how you can set on, if for example, you only had a 5km time, you could kind of progress it along. Bearing in mind that the shorter the distance is you’re using to predict, the more guessing is going on in between steps.

Probably the best place to guess from is your best half marathon and then somewhere in the region of eight if you’re extremely fit and get better with distance and about 15 seconds per km would be your normal drift off.

BB: Lindsey, it’s important obviously to know your marathon pacing because the last thing you want to do is realise at about 32km into a marathon that you’ve got a wrong. Having these calculations on what you should be running your marathon is important and like you say, there’s a bit of variation if you don’t have a 21km time, if you’re working it on your 5km time, but having these things and making sure that you stick to it is important if you’re going to achieve the marathon goal you set out to achieve?

Even splits is the key to a well paced marathon

LP: Absolutely. I think if you are aiming or in a marathon really what we’re trying to do, provided the two halves of the race are fairly similar in terms of profile and if you’re not dealing with extreme environments, like very, very cold or extremely hot, then we want to approach a marathon in a fairly even paced time.

Aiming to be at halfway no more than one and a half to two minutes faster in the first half than you intend to run the entire race and that, as you said, is why it’s important to stick to that plan because at the beginning of the marathon we can feel extremely fresh and good and feel like it’s our day and you push it really hard and then all of a sudden somewhere between 21km or 13 miles and 16 miles or 25km, that’s when you start to feel, oh-oh, I’ve overdone it and you’ve still got quite a lot of race left to go.

In a marathon, the last three miles or 5km really are telling and we can lose 30 seconds to a minute per km easily if our legs really have taken a hammering.

BB: You always say, and I always mess it up, I’m going to paraphrase it, you’re going to have to do it properly, but you are a firm believer that you’ll never make up enough time by going out too hard in the first half, that what you lose in the second, if you go out too fast. I think I’ve messed that up, but explain that in a bit more detail.

Starting slowing is the best way to pace a marathon

LP: I think the sentiment will be understood and that’s to say that I always say, you can never put enough time in the bag by going out too hard to save more than you’ll lose in the second half. You’ll always lose more in the second half than intended if you go out with that sort of strategy. I’d say it’s probably somewhere in the region of two minutes for every minute that you go through too fast through halfway, is what you’ll lose in the second half.

BB: That’s why It’s important to get the pacing right. I’ve tried the ‘go until you blow’ strategy, it’s not pretty. Definitely heed this advice to help you calculate your marathon pace. Lindsey, as always, great to catch up, don’t forget as well, if you want to win, all you need to do is check out our audio podcast.

We’re running a great promotion, it’s all part of the #BiogenJourney where we’re following James, ‘Hobbo’ Hobson’s journey to Ironman 70.3 and if you share your Biogen journey on the social media's, whether it be on Facebook, Twitter, Instagram, just use the hashtag, #BiogenJourney, tell us what you are training for and what you need help with and you could be winning access to the Coach Parry online training platform. It’s a phenomenal platform.

There are over 60 training programmes; you get access to Lindsey and the rest of our coaching staff in the forums. Strength and conditioning programmes, the works, so definitely go check that out as well. Use the hashtag, it is #BiogenJourney and we could be picking it up and making you a winner, so make sure to listen to our audio podcasts to find out if you are a winner.

Lindsey, as always, great to catch up, thanks for your time today, we look forward to catching up again next week.

LP: Chat soon Brad.