The HRM‍-Fit™ and HRM-Pro™ series accessories calculate your running pace and distance based on your user profile and the motion measured by the sensor on every stride. The heart rate monitor provides running pace and distance when GPS is not available, such as during treadmill running. You can view your running pace and distance on your compatible D2™ Mach 1 watch when connected using ANT‍+^® technology. You can also view it on compatible third-party training apps when connected using Bluetooth^® technology.

The pace and distance accuracy improves with calibration.

Automatic calibration

The default setting for your watch is Auto Calibrate. The heart rate accessory calibrates each time you run outside with it connected to your compatible D2 Mach 1 watch.

NOTE: Automatic calibration does not work for indoor, trail, or ultra run activity profiles (Tips for Recording Running Pace and Distance).

Manual calibration

You can select Calibrate & Save after a treadmill run with your connected heart rate accessory (Calibrating the Treadmill Distance).