I would like to see real-time data (speed and cadence, no heart-rate for now) on Strava Live on my iPhone 7. Do I need to install bluetooth sensors on my bike or it just magically works? If it just works, is it reliable/accurate or I should still install sensors and let it get this information from the bluetooth sensors?

  • To be honest - bluetooth is the wrong protocol for sensors. ANT+ is far more economic on battery and works fine. Bluetooth sensors use batteries 10 times quicker than the same ANT+ sensor, even BLE ones. But iphones are only bluetooth- to get ANT+ you need an adapter, or a Wahoo RFLKT, a garmin, or an android phone which do ANT+ natively. Comment because not an answer.
    – Criggie
    Apr 11, 2017 at 1:04
  • My previous comment is now 7 years old, and the world's moved on. BLE Bluetooth Low Energy improves battery life. There now exist android phones without ANT++
    – Criggie
    Jan 25 at 9:51

3 Answers 3


Strava (Premium) can determine your speed using GPS data, although GPS can be less accurate than a dedicated sensor because it jumps around a bit.

There's no magic way to determine cadence without a sensor, except maybe counting it in your head.

  • In the case of a fixed gear bike, you can determine cadence from speed and gearing information. So, you could in principle calculate it from the GPS data.
    – Batman
    Apr 10, 2017 at 16:03
  • You may want to add a note that without a "STRAVA PREMIUM" subscription, you only see average speed / cadence data for your ride. If you want instantaneous real-time data, you got to pony up. :-(
    – RoboKaren
    Apr 10, 2017 at 16:32
  • 1
    iPhone has accelerometer, so it might be possible to help speed measurements using the data. If you keep the phone in pocket, it could be even possible to extract cadence from the data.
    – ojs
    Apr 10, 2017 at 18:27
  • That's a good point about the accelerometer. I'm not sure how well it would measure speed, since your acceleration is the same at a constant 5kph as at 25kph, you'd have to keep a running sum of all accelerations which sounds very error prone. Cadence is a good point, somehow an iphone by default measures your steps, but at that point the phone becomes the sensor. And since you can't see the screen, you couldn't see the live data anyway. And of course as far as I know Strava currently does neither of these (it does use the barometer for elevation though).
    – Jamie A
    Apr 10, 2017 at 19:16
  • GPS speed is pretty accurate and consistent these days for reasonably steady state movement (e.g. road riding). It becomes an issue with fast direction changes e.g technical MTBing. Iphone has gps for speed, accelerometer (and Gyros) with GPS could be fed into a Kelman filter, but GPS is dgoo enuf' for many, and sensors are accurate and cheap for the rest - not sure its worth the effort trying to do it without sensors.
    – mattnz
    Jun 28, 2023 at 3:59

My understanding and research are based only on cycling(amateur). Not sure but may be imposed on running too.

I use the Zepp app(Amazefit iOS app) and have Amazefit GTS Mini 2 (cheap heart rate monitor). There is no cadence sensor in my smartwatch or cycle. But still, my Strava showed Cadence surprisingly.

In my humble research, I found that cadence meters and phone accelerometers work similarly (if not the same). I started recording in the Zepp app and kept my iPhone in my pocket while cycling. I'm pretty sure the accelerometer in the phone measured the cadence.

In the below pic, you can see the cadence is flat when the speed increases. This confirms that I'm moving downhill and hence I have stopped pedalling altogether. The flats in cadence are averaging the overall cadence, it is just showing that value instead of a zero (if I don't pedal cadence = 0)

First where phone in pocket

Now the zero/averaged cadence is either because I wasn't pedalling or the sensor didn't work. I had one more run where I attached the phone to the frame to check the map, in the below image, see the cadence is just spikes(not correct measurement) and averaged most part of it.

Second when phone attached to bike frame

So to answer, the cadence can be measured by the accelerometer in your phone if it's in your pocket, strapped to your feet. or shin :D. Strava doesn't use the accelerometer, so I imported the GPX file from Zepp and loaded it to Strava. This works pretty well. Is the phone a replacement for a Cadence sensor? No, but looking at the data if it works and with an error of 5-10% I'm happy to use my phone.

Special thanks to the post - https://www.mtbr.com/threads/cadence-data-in-strava-without-sensor.1130685/


Answer: No you might not need external sensors in Strava, at least for running cadence.

Strava's cellphone app now has some support for phone internal sensors for cadence. Some cellphones call it "steps per minute" or SPM or Running Cadence.

enter image description here
Nordic_HRM is a legitimate Bluetooth chest sensor, wheras Running Cadence is the internal sensor on this phone.

I got a month free of Strava premium and to my surprise there is now a cadence log from my run. It's a mess. Phone in shorts pocket, jogging I got very peaky readings between 130 and 175 spm, roughly the correct range. But doing mild intervals (73-77 per 300m) with walking rest, it gave 100-300 spm. I'm sure I never hit 200 even. Perhaps auto pause and bad logging logic made it worse.

I don't understand why the phone could not learn to pick up on the SOUND of foot steps. I bet it registers and is rythmical enough to be found in the mic data if only tried.

More info: https://www.mtbr.com/threads/cadence-data-in-strava-without-sensor.1130685/

Speed has always been available because it is calculated from GPS data.

  • Don't forget that Strava can probably infer running cadence from the phone accelerometers, but it has no means to measure cycling cadence on its own. Asking for access to the microphone would increase power drain, and don't forget that outdoors is noisy, so there would be an issue of signal to noise.
    – Weiwen Ng
    Jun 26, 2023 at 19:29
  • Hi, welcome to bicycles. I believe the question was about cycling speed and cadence, not running.
    – DavidW
    Jun 26, 2023 at 19:50
  • Welcome to the site - I'm going to tweak this answer a little in the edit Feel free to modify further if I change your intent.
    – Criggie
    Jun 27, 2023 at 22:22

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