CycleOps PowerCal review

Power estimation from heart rate

Our rating 
1.5 out of 5 star rating 1.5
GBP £85.00 RRP | USD $100.00

Our review

Not, in fact, a power meter
Skip to view product specifications

The PowerCal is a strap with an algorithm that converts your heart rate into an ANT+ watts signal. This can then be displayed on compatible computers, such as the Garmin Edge of CycleOps Joule.


On the plus side, it quantifies your effort on the bike, providing a real-time ‘wattage’ number as you ride and allowing for a full measurement of effort in any number of power software options.

On the negative side, it isn’t a power meter. The PowerCal doesn’t measure power, it guesses it, and in doing so doesn’t provide any realistic semblance of accurate power meter data.

For years, CycleOps has done a great job of providing reliable hub-based power meters at a reasonable cost. The PowerCal is an attempt to bring in some new customers at a very low relative price.

Part of the problem is simply presentation: if the PowerCal showed information called something besides ‘watts’ it could be more useful. Just look at the Nike FuelBand.

Quantifying effort without a real power meter is tricky. Strava has addressed this with a Suffer Score based on time spent in various heart rate zones. In the parallel field of running, TrainingPeaks has used a Training Stress Score based on time over pace, taking your top-end speed into consideration. And the iBike has undertaken to measure most of the forces opposing a cyclist, and doing the math to spit out a wattage number.

In a number of trials with the PowerCal, we found the ‘wattage’ numbers to be way, way off, both in the short term and averaged over 90-minute rides. Also, the corresponding summation metrics, such as kilojoules or Training Stress Scores, were also off by about 30 percent compared to files from the same ride with a power meter.

Looked at here in trainingpeaks, the peaks and valleys on the powercal wattage (above) were much more drastic than the actual power output:
Ben Delaney/Future Publishing

In TrainingPeaks, PowerCal’s number changes were much more drastic

There’s no way to adjust anything in the PowerCal’s algorithm. Whether you’re a 20-year-old fit woman or an 80-year-old man with one leg, the PowerCal spits out the same wattage number based on fluctuations in heart rate.


The concept – quantifying your effort on the bike without a power meter – isn’t a bad thing. But the PowerCal isn’t a power meter, and shouldn’t be presented as one.

Product Specifications


Name CycleOps PowerCal
Brand CycleOps

Batteries Included Yes
Type of Battery Required CR2032
No Of Batteries Required 1