How to determine your marathon race pace…

Deciding how to pace your goal marathon race is always a tricky one. You may be a first timer with or without a goal time, or an experienced marathoner with a specific target time, but at some point, you’re going to have to take stock of your training and racing to date and decide what pace you intend to set out and run 26.2 miles… this isn’t something you want to get wrong – too fast and you risk hitting the wall, too slow and you don’t do your hours of training justice. So how can you decide what to do?


There are several ways of tackling this, but first:


What is your goal?

For first timers, the target is often to get round in one piece without too much pain… so looking at a number of runs you have already completed, especially if near race distance (e.g. 16-20 miles) will give you a good idea of what pace you can sustain. If you’re not near race distance yet, you can use past race or run experience to extrapolate either by using a calculator or a formula (as discussed below).


If you have already done a marathon (or several) and want to improve on your current pace, you may already have a goal time in mind. You now need to reflect on how your training has gone, what sort of fitness level you are at, are you injured or niggly? Did you or are you struggling to sustain your paces in training? You also need to consider how much time you have left – the further away your race, the more ambitious you can afford to be, whereas if you’re starting the taper, don’t count on building fitness now.


There are various ways to help you set the right race pace for you:


Doing a test run at the proposed pace (or several): 
Decide on your distance, do a test run or couple of runs and see how your pace feels. A great way of doing this is to add  5-10 miles at that pace into a longer run (don’t do the whole long run at proposed marathon pace or you risk overtraining). The pace should feel reasonably comfortable for a good part of the segment (depending on how long you have until your target marathon) and you should be able to hold the pace throughout the segment. Slowing towards the end is a sign that you may have been too ambitious in your goal and perhaps need to reduce the pace a little (consider other factors too, like did you fuel well enough, is it poor weather, hilly or just a bad day – which is why several paced runs are better than one for this).
You can then use an online calculator to see what time you could finish if you run at that pace for your race.


Doing a race / using a calculator:

Doing a race is a great way of predicting a marathon time – longer races are more useful – e.g. a half marathon will be a better predictor than a 5k. Run your race hard and review your finish time. It does depend on how far out you are from your marathon, a hard half will be faster than marathon pace, so your target marathon pace will be slightly slower than that half time. For example, a 2 hour half marathon (9.09 min/mi) may equate to a 9.25-9.30 min/mi pace over the marathon. Some online calculators give an idea of what race times may translate to over different distances (a few are given at the end of this page to help). They vary in accuracy so try a couple, and remember, the nearer the distance of your test race to your target race, the more accurate the result.
Some people quote formulae to predict – you may have heard marathon times as double your half time and add 10-20 mins. For example, a 1.45 half time will double to 3.30, and so this runners target time may be 3.40-3.50 for the marathon. This can work but can also vary wildly depending on your speed, experience and training. A faster marathoner is likely to be much nearer the double and 10 mins than a slower marathoner who may need to double their time and add up to 40 minutes. The best thing to do is to use that pace as a starting point and test it out (see testing out pace on runs above).


Using Heart Rate (HR) data or perceived effort
This can be unpredictable but works for some. Remember HR and perceived effort can vary considerably depending on sleep, stress levels, elevation, weather, menstrual cycle, hydration levels, caffeine and other factors. HR data from training runs should be used rather than races because HR is often spiked by the stress of races, and make sure the source of your data is as reliable as possible (ie use a chest strap or equivalent where possible – wrist based monitors are not as accurate). Marathons are generally run in zone 3 – 70-80% of maximum HR for the majority. This is just below your lactate threshold (the point at which lactate accumulates in your muscles faster than you can remove it). You would expect your HR and perceived effort to increase through the race as your fatigue levels and effort levels increase. You can find out more about calculating your HR zones here:

Both HR and perceived effort are tough to use for longer races as when you’re well tapered, or nervous about your race, they can change. Remember – a race start is a stressful place for most of us and will cause increases in HR or perceived effort before you’ve even started.


Getting professional advice:
This is one of the best ways to decide on race pace, and can come in several forms.

  1. If you’ve followed a specific training programme that is aimed at finishing in a particular time, and you’ve nailed your training paces, this should help you decide.
  2. If you have a running coach, definitely discuss it with them!
  3. And of course you can ask online, and there are some amazing knowledgable people who can help, but don’t forget, they don’t know your training or running history, and whatever information you give online is just a snapshot, so make sure you weigh up any information or advice given very carefully.


Adjusting race pace
Once decided, you should stick to your race pace wherever possible, and make sure any reason for changing it is valid. If you haven’t already been that person that shot off too fast in the marathon, I’m sure you’ve heard horror stories of people who have. Don’t change your marathon goal pace because you feel great during the taper (yes, marathon pace does feel much easier when you’re well rested!), or at the start of the race (adrenalin does funny things to your decision making processes!). But on the other hand, don’t feel you have to stick to it rigidly if there is a good reason – hot or bad weather, niggles or feeling unwell all fall into this category.

I hope this was helpful to you in planning your upcoming marathon. Deciding on race pace is a tough call, but a review of your training and taking an evidence based approach is probably the best way to go. Whatever pace you’re running at, I hope your marathon is a positive and successful experience.


Have you already decided on your marathon pace for this autumn? Do you have any tips or stories about pacing that you can share? Or a reliable way of working out your pace? Please let us know…

Useful resources:
There are a lot more calculators available, this is just a few that my clients have used. They vary considerably so make sure you test out any suggested paces before committing, and do share any calculators or resources you use for predicting paces. calculator: good for using race data to work out equivalent finish times for different distances, and training paces:

McMillan calculator
Strava calculator: This is great for giving you splits for each mile – worth printing off and putting round your wrist etc. If going for a specific time
Runner’s World pace calculator: Good for calculating training paces –
Metathon – uses Strava data to predict a finish time. Most find this over-optimistic but it is interesting


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Martin Hulbert

Running Coach & Personal Trainer Leicestershire

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