Today, we are going to do an easy calculation. We're going to convert mile pace to kilometer pace. It's fun to calculate this by hand, but for convenience, you can also use the calculator and many others at runcalc.site.
Say we want to know how fast a 6 minute mile is in terms of kilometer pace. In other words, how much time does a runner need to run a kilometer if he or she needs 6 minutes for a mile?
First, we multiply 6 by 60. To go from minutes to seconds. 6 times 60 is 360 seconds to run 1609 meters (i.e. one a mile). Now, we divide 360 seconds by 1609, to get the number of seconds needed to run one meter. 360 divided by 1609 is 0.22.
The next step is to multiply that number by 1000, to get the number of seconds needed to run a kilometer. The result is 223.74 seconds.
The last step is divide this number by 60, to get from seconds to minutes. This one's a bit tricky, because we want minutes and remaining seconds. If you simply divide 223.74 by 60, you get 3.73 minutes, but obviously that's not what we want (Because we could ask: how much time is 0.73 minutes?) So we remember the 3 minutes, which is 180 seconds (that's 3 times 60). Now we take our original number, 223.74 seconds and subtract 180 seconds, resulting in 43.74. That's the number of seconds remaining, meaning that a 6 minute mile corresponds to a 4 minute and 44 seconds kilometer.
If you don't want to do this by hand, go over to runcalc.site and let the website do it for you.
Photo by i yunmai on Unsplash
Nathan hydration pack, © 
Running in Meatballs (1979), © 1979 Paramount Pictures
A friendly cow somewhere between Schipluiden and Schiedam