Connecting a Power Meter or Speed Sensor to a Smartwatch

Why connect a power meter or speed sensor to your smartwatch

A power meter measures your actual power output in watts, which is a more direct indicator of your effort than speed or heart rate. A speed sensor provides ground speed even in areas where GPS is unavailable, such as tunnels or indoor trainers. Attaching these sensors to your smartwatch puts the data on your wrist without needing to look at a handlebar-mounted phone.

For structured training, power data helps you gauge intensity more precisely than heart rate alone. Combined with heart rate, it can reveal efficiency and help plan your training load. The watch logs all sensor readings into a workout summary that you can review later. To understand how training load is calculated, see our training load article and VO2 max article.

The wireless protocols: Bluetooth and ANT+

Sensor communication relies on wireless protocols. The two most common in cycling sensors are Bluetooth and ANT+. Bluetooth technology includes a low-power variant, Bluetooth Low Energy (LE), which is specifically designed for small devices that run on coin-cell batteries. The Bluetooth technology overview states that the Bluetooth LE radio is "designed for very low power operation," making it suitable for sensors that transmit continuously for hours.

ANT+ is another low-power protocol widely used in sports equipment. Many multisport watches support both Bluetooth and ANT+, but not every watch does. Some budget fitness bands only offer Bluetooth. To connect a sensor, your watch and the sensor must share at least one common protocol. If you want a deeper dive into ANT+ compatibility, read our ANT+ smartwatch article.

What data does the watch record?

Once paired, the watch can receive power (in watts) from a power meter, speed from a speed sensor, and cadence (pedaling revolutions per minute) from a cadence sensor. Many sensors combine speed and cadence in one unit. This data appears in the workout view and is stored in the activity history.

Beyond sensor data, the watch records its own GPS position (if it has GPS), optical heart rate, time, and distance. When combined, these metrics allow for calculations like average power, normalized power, and training effect. For example, normalized power accounts for variations in power output, giving you a more accurate picture of the ride's intensity. These derived metrics are essential for serious cyclists who want to track progress over time. To learn more about these derived metrics, check our training load article and VO2 max article.

How to check compatibility before you buy

First, look at the watch's specification sheet to see which wireless protocols it supports. Common phrases are "Bluetooth Smart" or "ANT+". If the watch only lists Bluetooth, it will only pair with Bluetooth sensors.

Second, check the sensor's specifications to confirm its protocol. Many modern power meters support both Bluetooth and ANT+, but some older units only use ANT+. Third, consider software compatibility: some watches require a firmware update or a specific companion app before they recognize third-party sensors. Reading the manufacturer's compatibility list or contacting support before purchase can save you from a mismatch.

Also, keep in mind that even if the protocols match, the watch might only support certain types of sensor profiles. For example, a watch that supports heart rate sensors may not support power meters. Always verify that the specific sensor type is listed in the watch's capabilities. Some watches let you start a "Cycling" workout and then manually search for sensors. If the watch does not have a specific data field for power (watts), it may not be able to display or record that metric.

• Confirm the watch supports Bluetooth, ANT+, or both.
• Confirm the sensor uses one of those protocols.
• Check whether the watch's sensor profiles include power meters, speed, and cadence.
• Check for firmware updates or companion app requirements.

Pairing tips for a smooth setup

When you first power on a sensor, it usually enters pairing mode for a short window. Put the sensor close to your watch, start the watch's sensor search, and confirm the connection. Some watches display the device name and signal strength. If the sensor does not appear, try moving the sensor closer to the watch, ensuring it is charged, and restarting the pairing process on both devices.

After a successful pairing, the watch will remember the sensor for future workouts, so you do not need to re-pair every time. You can typically manage multiple sensors and assign them to specific sport profiles, such as a speed sensor for cycling and a separate one for running. This allows you to switch between bikes with different sensor setups without re-pairing each time.

Choosing the right smartwatch for sensor connectivity

If you plan to use a power meter or speed sensor, prioritize a watch that explicitly mentions support for these sensors. Sports watches typically offer longer battery life, physical buttons that are easier to use when wet or sweaty, and dedicated cycling modes. Browse our buying guides to find a watch that fits your needs.

For dedicated cycling training, many Garmin watches support both ANT+ and Bluetooth. If you prefer an Android-friendly option, Wear OS watches with Bluetooth LE can handle sensor pairing. For off-road or rugged use, a rugged GPS watch with ANT+ and Bluetooth gives you flexibility. Check the best Garmin smartwatches guide, the best GPS smartwatches guide, the best Wear OS smartwatches guide, and the best rugged GPS smartwatches guide to compare options.

What to pick for your use

Questions

My watch only has Bluetooth. Can it connect to an ANT+ power meter?

No. If the power meter only broadcasts ANT+ and your watch only supports Bluetooth, the two devices cannot communicate directly. You would need a watch that supports both protocols, or a protocol converter that translates between them.

Which is better, Bluetooth or ANT+?

Both are low-power wireless technologies. Bluetooth is more common in consumer devices, while ANT+ is often found in sports sensors. The best choice depends on what your existing sensors and watch support. Always ensure they share at least one common protocol.

Will connecting a power meter drain my watch battery faster?

Bluetooth LE and ANT+ are both designed for low power consumption, so the impact on battery life is usually minimal. Continuous data streaming does increase power usage slightly, but it is much less than GPS or an always-on display.

Can I use my phone as a relay between the sensor and the watch?

Some watches can receive sensor data indirectly through a phone app, but this is less reliable and can introduce latency. Direct pairing between the watch and sensor is the preferred method. Check the watch's documentation to see if it supports relayed data.

Do all smartwatches support external cycling sensors?

No. Many basic fitness trackers lack support for external sensors. Only watches that explicitly list ANT+ or Bluetooth sensor profiles for power meters, speed, and cadence will work. Always review the specifications before buying.

How do I know if my sensor is paired already?

Most watches show a sensor status icon on the watch face or in the workout app. You can also go to the settings or connectivity menu to view connected sensors. A paired sensor usually reconnects automatically when the watch is in range.