π Running Pace Calculator
Find your pace per km and per mile, speed, and predicted race times from any run.
Your Pace
These are estimates for planning and education only, not medical advice. Talk to a qualified professional before changing your training or health routine.
How to Use This Calculator
Enter the distance and time from any run, training or race, and the calculator returns your pace, speed, and predicted times for the classic race distances.
Enter the distance you ran and choose kilometers or miles.
Enter your finishing time in hours, minutes, and seconds. Leave hours at 0 for shorter runs.
Read your pace per km and per mile, plus your average speed in km/h and mph.
Use the Riegel predicted times for 5K, 10K, half marathon, and marathon to set training and race goals.
The Pace, Speed, and Riegel Formulas
Pace and speed are two views of the same run. Pace tells you how long each kilometer or mile takes, which is what most runners watch during a workout. Speed tells you how far you cover per hour, which is more intuitive for comparing efforts across very different distances. The Riegel formula then extends one known performance to other distances. The exponent 1.06 captures the fact that sustainable pace fades as distance grows, so a marathon prediction always comes out slower per mile than the 5K it was built from.
Worked Example
You run a 5K in 25:00. Pace = 25 minutes / 5 km = 5:00 per km. Since 5 km equals 3.1069 miles, pace per mile = 25 / 3.1069 = 8:03. Speed = 5 km / (25/60 hours) = 12.0 km/h, or 7.46 mph. Marathon prediction with Riegel: T2 = 1500 x (42.195 / 5)^1.06. The distance ratio is 8.439, raised to 1.06 gives 9.591, so T2 = 1500 x 9.591 = 14387 seconds = 3:59:47. That 9:08 per mile marathon pace versus the 8:03 per mile 5K pace shows exactly how the formula models endurance fade.
Using Predictions in Training
Treat predictions as a planning range, not a promise. They assume similar conditions: flat course, good weather, proper fueling, and training appropriate for the target distance. A 5K-based marathon prediction is the least reliable jump in the table; if you want a sharper marathon target, feed the calculator a recent half marathon or a long tempo run instead. For workouts, many coaches anchor training paces to these predictions: easy runs well below 5K pace, tempo work near the predicted 10K to half marathon effort, and intervals above 5K pace. Build up gradually. These are estimates for planning and education only, not medical advice. Talk to a qualified professional before changing your training or health routine.
Frequently Asked Questions
What is a good running pace?
It depends on your fitness and the distance. Many beginner runners hold 7:00 to 8:30 per km (about 11:15 to 13:40 per mile) on easy runs. Intermediate runners often run easy days at 5:30 to 6:30 per km (8:50 to 10:30 per mile) and race a 5K under 25:00. Rather than chasing someone else's number, compare your current pace to your own past runs on the same route.
How do I convert pace between minutes per km and minutes per mile?
Multiply a min/km pace by 1.609344 to get min/mile, or divide a min/mile pace by 1.609344 to get min/km. Example: 5:00 per km x 1.609344 = 8:03 per mile. This calculator does the conversion automatically, so you never have to do the math by hand.
What is the Riegel formula and how accurate is it?
The Riegel formula predicts race times across distances: T2 = T1 x (D2 / D1)^1.06. It was developed by engineer Peter Riegel in 1977 from world-record data. It is most accurate when the two distances are close, for example predicting a 10K from a 5K. Predictions get shakier for big jumps, like marathon times from a 5K, because endurance, fueling, and pacing strategy matter more over longer distances.
Why is my predicted marathon pace slower than my 5K pace?
Because nobody can hold 5K effort for 42.2 km. The Riegel exponent of 1.06 models the natural fade in sustainable pace as distance grows. A 25:00 5K runner predicts about 3:59:47 for a marathon, which is 9:08 per mile, well off the 8:03 per mile 5K pace. That gap is normal and it is why marathon training focuses on endurance, not just speed.
How should I use pace in my training?
A common structure: easy runs 60 to 90 seconds per mile slower than your 5K race pace, tempo runs near the pace you could hold for an hour (roughly your predicted 10K to half marathon pace), and intervals faster than 5K pace with full recoveries. This calculator's race predictions give you realistic target paces for each workout type.