Pace and race tools
Each tool answers a different question, and they share the same arithmetic. If you are not sure which one you want: the pace calculator converts a time into a pace, the charts list every finish time with the pace it needs for one distance, the VDOT calculator turns a race result into training intensities, and the predictor moves a result from one distance to another.
Every page here shows pace in both kilometres and miles, and every formula is documented on /sources with its primary source.