No smart trainer? Ride anyway

A basic fluid or magnetic trainer plus an inexpensive Bluetooth speed sensor is all you need: the game estimates your watts from wheel speed using published trainer curves.

Monsoon Cycles, Colorado Springs · Updated August 16, 2026

Smart trainers are wonderful and expensive. The classic answer, the one Zwift was built on in 2015, still works: put your bike on any dumb trainer, strap a Bluetooth speed sensor to the wheel, and let software turn wheel speed into estimated watts. We publish the exact curves we use, so you know precisely what the estimate is doing.

The three-step setup

1. Mount the bike on your trainer and set the roller tension the same way every ride, because the curve assumes consistent tension.
2. In the game, tap CONNECT SPEED/CADENCE and pick your sensor (CatEye, Wahoo, Garmin, any Bluetooth CSC sensor works).
3. Under MORE, choose your trainer curve (magnetic light, medium, heavy, or fluid) and your wheel size from the 23-size list.

That is it. Estimated power will track within roughly 10 percent of a real power meter on a consistent setup, which is plenty for training rhythm, segment hunting, and having a great time.

Questions riders actually ask

How accurate is virtual power?

On a consistent setup, within roughly ten percent of a real power meter, with the biggest error at very high wheel speeds. It is consistent with itself, which is what matters for training.

Which sensors work?

Any Bluetooth LE speed or speed-and-cadence sensor using the standard CSC service: CatEye, Garmin, Wahoo, Magene, and most others.

Does iPhone work?

iPhone Safari cannot talk to Bluetooth sensors from a web page. Demo mode and .fit replay work on iPhone; for live sensors use a laptop with Chrome or Edge, an Android device, or the Bluefy browser app on iOS.