ResultsHQ has two different Handicap (HC) formulae built into it for calculating Time and Distance HC values for athletes. Here is the description of the formulae used:
Get X amount of latest results.
Calculate difference between each result and the best result for that event
Subtract the difference from the backmarker value
Round up or down to the nearest X second.
Take average of X results for final HC time.
Get the best athlete speed based on event distance and best pb
Get the difference between the athlete speed and best athlete speed
Calculate the start difference based on the speed difference