The calculator below is a simple web app that allows you to input your time from various races and see the equivalent paces on a single graph.
Why would you want to do this?
This is one way to diagnose your strengths and weaknesses as a runner. If your short distance results – like in a mile or 5k – are relatively stronger than your long distance results – like a half marathon or a marathon – it’s a sign that you need to work on your aerobic development and/or lactate threshold.
It’s always a way to help estimate your race pace. There are lots of calculators out there to convert one race – like a 5k or 10k – to a marathon pace. But if your pace drops off at longer distances, you’ll want to be more conservative in your pacing.
Conversely, if your long distance results are equivalent to or stronger than your short distance results, you would likely benefit from implementing more speed work in the form of short, intense intervals.
Race Pace Comparison Tool
How This Calculator Works
This calculator is built on the premise that your performance across different distances should be related – such that the finish time from one race should predict your finish time in another.
There are a number of different methods for making these calculations. This calculator relies on a formula that Pete Riegel devised in the 1970’s. The expected finish time in one race can be estimated from the known finish time in a different race, based on the ratio of distances between the two races raised to a constant exponent.
When you enter a finish time for a specific race – like a 5k – it is then converted into equivalent finish times for other races. By default, the calculator uses the mile, 5k, 10k, half marathon, and marathon. You can adjust this in the settings.
Then, those equivalent race times are divided by their race distances to yield an estimated race pace. By default, this is expressed in minutes per mile, but you can switch that to minutes per kilometer in the settings.
Each set of paces is plotted on the graph, and the color of the line denotes which race time the estimates are based on.
In theory, you could also do this without converting the times to paces. However, this results in a y-axis that quickly becomes out of control. By converting the equivalent race times to paces, you can plot multiple different paces on a small vertical range.
Once you’ve entered multiple race times, a summary is printed at the bottom identifying which distance is your strongest effort and which is your weakest. The difference between those efforts is also categorized as normal, medium, or large – based on how big the difference is in the predicted marathon finish time. These categories are rough approximations, and feel free to make your own judgement about what constitutes a meaningful difference.
Note that for this to be most useful, these times should be recent race times and they should represent an all out race effort or time trial. If adverse conditions impacted your time – like excessive heat or a hilly course – that may influence the results. If the race time is several years old, that could also make the comparison less reliable.
How to Adjust the Settings
The “Distance” dropdown lets you select which race distance to enter.
The standard race distances are 1 Mile, 5K, 10K, Half Marathon, and Marathon. However, you can also select “Custom…” to enter any other race distance. When you do so, select “mi” (for miles) or “km” (for kilometers) and then enter the distance.
The “Races to Compare” option lets you change how many race times you can input.
By default, you can enter two races – a 5K and a 10K time. You can change the settings to allow up to five different race times.
The “Pace Unit” option lets you toggle between Min / Mile (minutes per mile) and Min / Km (minutes per kilometer). I’m American, so I think in minutes per mile … but I know many people prefer kilometers.
How to Interpret the Results
Once you’ve graphed multiple race results, you want to look and see how close or far apart the lines are.
For example, let’s say you graphed 5:00 for the mile, 18:00 for the 5k, and 3:15 for the marathon.
The strongest relative effort – the lowest line on the graph – is the mile. The weakest relative effort – the highest line on the graph – is the marathon. The 5k line is in the middle.
This pattern would represent someone who has a lot of speed but little endurance. Perhaps they were a sprinter or an explosive athlete. They can run fast over shorter distances like the mile. But they lack the stamina and endurance to convert that time to longer distances.
A 5:00 mile should convert to a ~5:21/mi 5k. So an 18:00 (5:47/mi) 5k is much slower than predicted. This athlete would likely benefit from threshold work and race-specific intervals.
Similarly, a 5:00 mile should convert to a ~6:04/mi marathon pace. Short distances don’t always convert properly to long distances, so you should take this with a grain of salt. But that’s a long way from the 7:26/mi pace of a 3:15 marathon.
A person who can run a 5:00 mile should be able to run a marathon much more quickly than 3:15. If that were their actual time, they’d likely want to focus on increasing their total volume and spending more time at threshold and marathon pace.
If the lines are clustered relatively close together, then you’re a much more balanced runner. Continued improvement will likely require a balanced approach – a little bit of increased volume and a little bit of increased intensity. Switching between the two of the course of the year would be a wise approach.
You may also want to refer to this post on how to understand relative race times.