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Cadence — how many pedal revolutions per minute you’re turning — is one of the few training numbers that’s both easy to measure and genuinely useful, whether you’re chasing efficiency on long rides or trying to spare your knees on a hilly climb. Most modern bike computers and watches can display cadence, but they don’t all get the number the same way, and the method matters for accuracy, setup hassle, and what else you get bundled in. We compared the three real approaches riders actually use: magnet-based sensors, accelerometer-based sensors, and power meters with built-in cadence.
Option 1: Magnet-Based Cadence Sensors
The Garmin Cadence Sensor 2 (around $40) is the classic approach: a small pod straps to your crank arm and a magnet on the frame triggers it once per revolution. It’s dead simple, dirt cheap, and the battery (a standard CR2032) lasts a year or more of regular riding. The catch is installation — you have to position the magnet and sensor close enough to trigger reliably, which usually means zip ties and a few minutes of trial and error, and it can work loose or drift out of alignment on rough roads. Once it’s dialed in, though, magnet sensors are about as accurate as cadence measurement gets, since they’re literally counting physical revolutions rather than inferring them.
Option 2: Magnetless (Accelerometer) Sensors
Wahoo’s RPM Cadence sensor (around $40) and Garmin’s newer magnetless cadence sensors skip the magnet entirely, using an accelerometer to detect the pedaling motion directly from the crank arm’s movement. This is the setup most riders should default to now: no alignment fuss, no magnet to knock loose, and accuracy that’s essentially identical to the magnet-based version for steady pedaling. The one place it can lag is in the first second or two after you start pedaling from a dead stop, since the accelerometer needs a moment to recognize the rotational pattern — magnet sensors register the very first revolution instantly. For anything but track-standing intervals, that’s a non-issue.
Option 3: Power Meters With Built-In Cadence
If you already own or are shopping for a power meter — a Stages, 4iiii, or Favero Assioma, for example — you likely don’t need a separate cadence sensor at all, since crank- and pedal-based power meters derive cadence from the same strain-gauge data they use for power. This is the most convenient option in the sense that it’s one less pod to buy, pair, and charge, and the cadence reading is tightly synced with your power numbers on the same data stream, which matters if you’re analyzing power-to-cadence relationships (like finding your most efficient climbing cadence). The downside is cost: buying a power meter purely to get cadence would be a wildly expensive way to answer a simple question, so this option only makes sense if power measurement is already on your list for other reasons.
Comparison Table
| Option | Price | Setup | Best For |
|---|---|---|---|
| Magnet-Based | Around $40 | Fiddly alignment | Budget riders who don’t mind setup |
| Magnetless (Accelerometer) | Around $40 | Strap and go | Most riders — the default pick |
| Power Meter Cadence | Around $300–$1,000+ | None extra if you own one | Riders who already track power |
FAQ
Do I need a cadence sensor if my bike computer already estimates cadence from GPS speed?
No GPS unit actually estimates cadence from speed alone with any reliability — if your head unit is showing a cadence number without a paired sensor, it’s either using your phone’s motion sensors (rough estimate) or you have a sensor paired that you forgot about. For real numbers, use a dedicated sensor.
Will a magnetless sensor work with an old head unit?
As long as your computer supports ANT+ or Bluetooth cadence broadcasts (essentially anything from the last decade), yes — the sensor type doesn’t change the pairing protocol.
Is higher cadence always better?
Not universally — most endurance cyclists land in the 85–95 rpm range as a sweet spot between muscular and cardiovascular load, but your ideal number depends on your fitness, terrain, and gearing. The sensor’s job is just to show you what you’re actually doing so you can experiment.
Verdict
For nearly everyone shopping today, a magnetless cadence sensor like the Wahoo RPM is the right call — it’s the same price as the magnet version with none of the alignment headaches. Only go magnet-based if you’re replacing a sensor you already have working, and only skip a standalone sensor entirely if a power meter is already in your plans for other reasons.
