Running Pace Calculator with Race Predictions and Heart Rate Zones
Work out your pace and speed from distance and time, your finish time from distance and pace, or how far you can run in a given time at a given pace. The calculator also lists predicted times for 5K, 10K, half marathon and marathon at that pace, and builds heart rate training zones with the Karvonen method from your age and resting heart rate. Everything runs in your browser and nothing is sent to a server. To add up split times, try the Time Calculator.
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Heart rate zones (Karvonen method)
Notes
- Predicted times assume you can hold the same pace throughout. In reality pace drops over longer distances, so treat marathon and ultra estimates as rough guides.
- Estimating max heart rate as 220 minus age varies a lot between people and can be off by 10 bpm or more. The zones are a guide, not medical advice.
- If you have a medical condition, are new to exercise, or feel palpitations or chest pain, talk to a doctor about training intensity.
- Pace is always entered per kilometer, even when you choose miles for distance.
Glossary
Pace
The time it takes to cover one kilometer (for example 5:30 per km). It is the inverse of speed, so a faster pace is a smaller number.
Karvonen method
A way to set target heart rates that accounts for resting heart rate: (max HR − resting HR) × intensity + resting HR. It reflects individual differences better than a percentage of max HR alone.
Heart rate reserve
The difference between your maximum and resting heart rate. The Karvonen method multiplies this reserve by the training intensity to get a target heart rate.
FAQ
How do I convert pace per km to speed in km/h?
Divide 3600 by the seconds per kilometer. A 5:00 per km pace is 300 seconds, so 3600 / 300 = 12 km/h. This tool shows both from a distance and a time.
How accurate are the predicted race times?
They simply multiply your pace by the distance, assuming you hold it the whole way. Pace usually drops over longer races, so applying a 5K pace to a marathon will look too fast. Allow some margin for long distances.
What is the Karvonen method?
It sets target heart rates using your resting heart rate. Max HR is estimated as 220 minus age, then target = (max − resting) × intensity + resting. It reflects differences in resting heart rate better than a plain percentage of max.
How should I measure my resting heart rate?
Count your pulse for one minute right after waking up, before getting out of bed. Averaging a few mornings gives a steadier number. A smartwatch resting heart rate value also works.
Can I enter pace per mile?
Distance can be in km or miles, but pace is entered per kilometer. The result also shows the pace per mile.
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