Running Pace Calculator

Pace is simply time divided by distance, and it is the number runners actually train against: minutes and seconds per kilometre or per mile. Speed, its inverse, tells you how far you go in an hour; pace tells you how long each unit takes. Most runners find pace easier to hold in their head, because a target like 5:00 per kilometre stays constant whether you are running a 5K or a marathon.

This calculator converts between the two systems. Enter any distance and time and it returns your pace in both kilometres and miles, plus your average speed. Because a mile is 1.609 kilometres, your per-mile pace will always be a larger number than your per-kilometre pace — the same effort expressed in different units. Switching between the two is useful when you follow a plan written in miles but race on kilometre markers, or vice versa.

The race predictions use the Riegel formula, which assumes that as distance roughly doubles, time increases by a factor of 2 raised to the power 1.06. In plain terms, endurance fades slightly as distance grows, so doubling the distance takes a little more than double the time. The exponent was fitted to real race results and holds well from about a 5K up to a marathon, which is the range where it is applied here.

Two caveats. Riegel assumes you are equally trained for both distances, which is rarely exactly true — someone with a strong marathon background will beat the prediction at long distances, while a speed specialist will beat it at short ones. And these are predictions, not promises; heat, hills and the day itself all move the number. Still, for setting realistic goals before a first half or full marathon, it is far better than a guess.

This calculator returns estimates for general information only. It is not medical advice, diagnosis or treatment, and it cannot replace an assessment by a qualified health professional. Individual results vary, and figures such as calorie needs, body-fat percentage and heart-rate zones are approximations based on population averages rather than measurements of you.