# zPower

> zPower is Zwift's estimated power calculation for supported wheel-on trainers that don't transmit power data (often called "classic trainers")...

Source: https://support.zwift.com/en_us/zpower-r1XjaXbxr

Last updated: 2026-07-08T19:59:39.113Z

# zPower

## What is zPower

zPower is Zwift's estimated power calculation for supported wheel-on trainers that don't transmit power data (often called "classic trainers").

To use zPower, connect either a power meter or a speed sensor with Zwift. Zwift uses data from the paired device to estimate your power output.

## Things to Know

*   zPower is an estimate of your power output and doesn't represent actual power values. Because the calculation depends on multiple variables, the power shown in Zwift may differ from the power you're generating.
    
*   While adding a power meter to your setup will give you more accuracy, a direct drive trainer provides the most accurate Zwift experience.
    
*   zPower isn't available in Zwift-organized events.
    
*   Adding a cadence sensor can improve accuracy.
    

## Best Practices for Using zPower

### Trainer

*   Select the correct trainer in Zwift.
    
    *   Zwift trainer names are based on the trainer's physical appearance, not the model name.
        
*   Tighten your trainer according to the hardware manufacturer's instructions.
    
*   If your trainer has a manual resistance dial or knob, set it to match the value shown in Zwift when connecting to Zwift.
    
*   If you're using a Mag trainer with a resistance setting cord, lay the cord flat on the ground.
    
    *   A resistance setting cord that isn't flat can affect your trainer's resistance.
        

### Tires

*   Inflate your tires to the recommended PSI.
    
    *   Under-inflated tires may cause inaccurate readings.
        
*   If possible, select the exact tire size from the Hardware tab in your in-game settings.
    
    *   Select the closest possible option, if your tire size isn't listed in Zwift.
        

### Speed Sensor

*   Position the tire magnet close to the speed sensor.
    
    *   If the tire magnet is too far from the speed sensor, the sensor may not detect each pass, which can cause inaccurate readings.
        
*   Make sure the speed sensor has sufficient battery power. Replace the batteries if needed.
    

## Related Articles

*   [Compatible Cycling Hardware](https://support.zwift.com/en_us/compatible-cycling-hardware-BkPlq7gr)
    
*   [Connecting a Speed Sensor](https://support.zwift.com/en_us/connecting-a-speed-sensor-ryZdj7beB)
    
*   [Connecting a Power Meter](https://support.zwift.com/en_us/connecting-a-power-meter-Bk7hoXWlS)
    
*   [Compatible Trainers](https://support.zwift.com/en_us/compatible-trainers-BkPlq7gr)
    
*   [Tire Size Conversion Chart](https://support.zwift.com/tire-size-conversion-chart-HyH6NiQckg)
    
*   [Finding zPower Events](https://support.zwift.com/en_us/preview/article/finding-zpower-events-ByGKVm3QGl)
    

Ride On.

\-The Team at Zwift