Here’s a link to a blog on calculating running power and relating that to expected race time:
https://blog.stryd.com/2020/01/10/ho...-target-power/
About one-third of the way down is an equation that estimates race time based on distance and target power during the race, expressed in SI units.
From this, I derived 27.9 as the product of a runner’s pace in minutes per mile and target power ratio in Watts/kg. Similarly 17.3 would be the product of a runner’s pace in minutes per km and Watts/kg.
Otto