Three Essential Running Calculators That Help You Conquer Your Marathon

The marathon calculator page contains several useful running calculators.

They are:

Race Conversion Calculator - You can use a recent race performance to estimate your marathon running time. Important to ensure you don't go out too fast!

Marathon Training Pace Calculator - Use your goal marathon time to establish the running training paces that align to that goal time.You can also use this calculator in reverse to work out a likely marathon performance based on your current running training times for easy runs, tempo runs etc.

Marathon Race Pace Chart - Based on your marathon goal time you can get a pace chart. This pace chart assumes negative splits, so it's a bit different from what you usually see on running websites. Worth checking out and worth reading the additional info supplied.

Every running calculator comes with its own little set of explanations.

Do yourself a favor and make sure you read the instructions coming with each calculator. You need to understand the usability and the limitations of these running calculators.


Running Calculator #1: Race Conversion Calculator

Race Conversion Calculator
The race I ran had a length of	MilesKilometres
Use dots, no commas. So 26.2 miles, not 26,2...
My time was (hh:mm:ss)	: :
Press the button, don't click Enter
Predicted time for your next marathon (hh:mm:ss) :

The Small Print of the Race Conversion Calculator

When using this calculator you need to consider a few things.

Longer races are better predictors - It almost goes without saying that  for marathon prediction the race you use as a predictor needs to be long enough. 5k is too short, 10k is so-so, 15k is getting there and a half marathon and above is really useful. Don't rely on shorter races alone. The outcome of a short race usually provides you with an overly positive marathon time prediction.

Use a recent performance - Also pretty obvious is that you need to pick up a recent race performance. Don't rely on a personal best of a year back to establish a marathon goal time. Your recent performance and current fitness is what counts.

Back it up with the right running training - The most important element is to make sure you back it up with the right running training. Endurance is key in the marathon. Many of us, I'd say 90-95% of us, falter in the last part of the marathon. Usually because we haven't done enough 20-milers and runs over 90 minutes.

Interested in doing the race conversion for any type of race, not just the marathon? Then simply go to the Race Conversion Calculator page.



Running Calculator #2: Running Training Pace Calculator

Marathon Running Training Pace Calculator
What is the goal marathon time?		: : (hh:mm:ss)
Press the button, don't click Enter
Corresponding marathon running training paces
Easy Pace :		/ mile	/ km
Tempo Pace :		/ mile	/ km
Interval Pace :		/ km	/ 400 m
Fast Reps :		/ 200 m	/ 400 m

Small Print of the Marathon Training Pace Calculator

The marathon running training pace calculator is a little bit more complicated.

And you need to use it with care. 

You can use it in two ways.

1. Use a marathon goal time to calculate corresponding running training paces.

Suppose you'd like to run your marathon in a certain time.

Based on that marathon goal time the calculator then calculates the corresponding running training paces for you.

So, if those times are in fact close to your running training paces, then the estimate would be that you could reach your goal time.

BUT.... you can't just force yourself to start running much faster in training! That is a certain road to injury. These running training paces need to come to you naturally. Well, naturally, due to doing your running training!

Example. Suppose you'd like to run a 3:59 marathon.
This provides you with:
Easy pace of 6:20 min/k (10:12 min/mi)
Tempo running pace of 5:17 min/k (8:31 min/mi)
Interval pace of 1:57 / 400m (4:53 min/km)
Reps pace of 1:46/400m (53sec/200m)

Suppose your current easy pace is 6:30 min/km, not 6:20 min/km. Well, first of all, you aren't too far off from your goal.

However, you shouldn't start pushing yourself to run 6:20 min/km instead. No, due to diligent training your easy pace will get faster over time. Only when your "natural" easy pace is 6:20 min/km, then 3:59 becomes a reasonable goal.

You also need to make sure that not just your easy pace lines up. Your tempo pace AND interval pace need to be "right" as well.


2. Work out your likely marathon time based on your current running training paces.

An alternative method of use of this calculator is to work out a likely marathon time, based on how fast your running training is at the moment.

When you train regularly, you probably know what your easy pace, tempo pace and interval running pace are.

Now, with a bit of trial and error you can work out what the corresponding marathon time is with those running training paces.

Example. Suppose your easy pace is 5:30 min/km and your marathon is three weeks away. Then what would be a reasonable marathon time to shoot for?

Well, let's try a few different times.

Let's enter 3:40 (3 hrs and 40 min) for our marathon. The easy pace that rolls out is 5:52 min/km.

Then, let's enter 3hr30. The easy pace becomes 5:36 min/km.

So now, let's enter 3hr20. The easy pace becomes 5:21 min/km.

Then 3hr25. Easy pace is then 5:29 min/km.

Just for completeness, let's then enter 3hr26. The easy pace is exactly 5:30 min/km.

So you see, you can quite quickly find the marathon time that corresponds with a certain training pace.


Make sure that all your running training paces line up to the same type of performance. Your easy runs may provide you with a prediction that you can run a 3 hr 26 min marathon. But your tempo runs may indicate a 3 hr 50 min marathon. It's almost always so that you need to rely on the slower outcome, not the faster one!


Running Calculator #3: Negative Split Running Pace Chart

Marathon Running Pace Chart (Negative Splits)
What is the goal marathon time?		: : (hh:mm:ss)
Press the button, don't click Enter
Time for First Half:		Pace: / mile	/ km
Time for Second Half:		Pace: / mile	/ km
Mile Splits		KM Splits
4 Miles		7 km
8 Miles		14 km
12 Miles		21 km
Half Way Mark		Half Way Mark
16 Miles		28 km
20 Miles		35 km
24 Miles		42 km
Finish Time		Finish Time

Small Print of the Marathon Pace Chart Calculator

a) This marathon pace chart assumes negative splits

b) This marathon pace chart does not provide splits for every mile/km

More and more people are catching on to the idea that running with negative splits (first part of the race slower than the second part) is a good idea for the marathon.

There are many benefits to running your marathon this way.

It protects you from starting off too aggressively. Especially if you happen to have a bad day. It provides a massive boost in confidence and a lot of motivation to be hunting down runners and to be passing dozens and dozens and dozens in the second half. And it mimics how many world records have been set.

To the second point, the reason I am not providing splits for every km / mile is that most races are not exactly flat or allow for exact even splits for every mile / km.

I think it makes more sense to split it up in the way I have done.

Hope these calculators have been useful to you.

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