What this calculator measures
Running pace tells you how fast you are covering a given distance. Tracking pace over time is one of the clearest indicators of improving aerobic fitness and running economy. It also helps you structure training at the right effort level — too fast on easy days increases injury risk; too slow on quality days limits adaptation.
How this calculator works
Pace (min/km) = total time in minutes ÷ distance in kilometres. Speed (km/h) = distance ÷ hours elapsed. The 5K projection extrapolates from your current pace using Riegel's endurance formula, which accounts for the fact that average pace tends to slow as race distance increases. Short distances may not project perfectly to longer distances without additional context.
How to use your result
Use your easy-run pace to set a ceiling for your Zone 2 runs (the heart-rate zones calculator can guide this further). Use race-pace estimates for structured interval and tempo workouts. Track monthly improvements in pace at the same perceived effort level as one of the best measures of aerobic progress.
Important limitation
Calculator results are estimates. Pregnancy, eating disorders, medical conditions, injuries, or concerning symptoms require qualified professional guidance.