How is cadence calculated?


Zwift has really changed the way I ride indoors (although I really long for spring right now, sick and tired of the gravel, snow, ice, rain, dirt and angry motorists on my daily commute to work…) and the introduction of Zwift on iOS makes it a lot easier to get started compared to when I used my laptop. However, I miss my Garmin ANT+ crank cadence sensor, because the calculated cadence seems a bit shaky IMHO… How is it even possible to calculate cadence and how does it work?

I use a Tacx Vortex Smart (just realizing that this question perhaps should be addressed to Tacx?)


The cadence is “estimated” by measuring the “pulses” in your pedaling, i.e. the less smooth your pedaling style is, the more accurate the cadence figure comes out.

When I first started using a PowerTap wheel for power I continued to use my Garmin cadence sensor.  I was getting all kinds of wild points on cadence.  I switched to using the PowerTap for cadence (which you would think is less accurate) and life got better.  I can only assume the issue was with having multiple ANT+ sensors