Race Time Estimator
Use the estimator below to translate a known race performance to a performance over any distance.
The algoithm was devised by Pete Riegel, a research engineer and marathoner, and published in Runner's World, most recently by Owen Anderson in 1997. It has been widely used since then. The formula is T2 = T1 x (D2/D1)f where T1 is the given time, D1 is the given distance, D2 is the distance to predict a time for and f is a factor which is 1,06 for distances less than 13 miles, 1.09 for less than 20 miles and 1.12 for greater distances. The factor reflects the drop of in speed over distance.