The running calculator uses the distance and finish time of your most recent race to approximate your current level of fitness. Your fitness level is then converted to an equivalent 10K time, for easy comparison with other race results at different distances. The conversion is based on equivalent fitness, not equivalent pace. The same level of fitness corresponds to successively slower average paces as the race distance increases. For example, a 24:05 5K (7:45/mile) corresponds to the same level of fitness as a 49:58 10K (8:02/mile).
Once your current fitness level has been determined, it can be used to predict your race times at other distances. The closer the other distance is to the original race's distance, the more accurate the prediction will be. Due to differences in physiology and training, some people may be better at longer distance races than shorter ones or vice-versa, but the calculator should yield accurate results for most runners. The recommended training paces are also determined from your current fitness level.