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You pedal. It sets the watts.

ERG control of your smart trainer, workouts scaled to your own fitness, and a readiness call from your sleep and HRV. Free.

Download on the App Store Get it on Google Play

Free, paid for by ads. Nothing to buy. · No account needed.

Everything else the ride needs.

Got 45 minutes? Here’s your loop.

Loops from your door, sized to your time
Every turn called, on maps for anywhere on Earth. No signal needed
Wandered too far? Tap back — home by the time you set
The weather, wind and air quality you’re heading into

Loop options in Kardiacs, each with its distance, time, climb and effort laid out

Directions in Kardiacs: a route to a dropped pin drawn on the map, with its distance, time and climb

You pedal. It sets the watts.

ERG control of your smart trainer
Workouts scaled to your fitness, indoors and out
Build your own, down to the interval
On your wrist with Apple Watch. A mix matched to every interval’s cadence (iPhone)

An indoor ride ready to start in Kardiacs, with the trainer and power meter connected and the target power shown

Structured indoor rides sorted by intensity, with interval charts and target power

Rest day or hard day? It knows.

Readiness from sleep, HRV and stress
Every session analysed — power, pace, zones
Fitness and fatigue over time

A daily readiness recommendation in Kardiacs, based on recent sleep, HRV and stress

A session summary in Kardiacs: pace chart, splits, and time in each zone

One app, not five.

Bike intercom
Trainer app
Route planner
Recovery tracker
Offline maps

All in Kardiacs. Free.

Ride in a minute.

Download. No account, no sign-up wall.
Tell it your age and weight — or connect Health — for zones from day one.
Pick Explore, Commute or Indoor. Go.

Bringing history? Import your Strava or Garmin archive, or any FIT file.

Why is it free?

Free, paid for by ads. Nothing to buy. The ads pay for the maps and servers.

Ride in a minute.

Download. No account, no sign-up wall.
Tell it your age and weight — or connect Health — for zones from day one.
Pick Explore, Commute or Indoor. Go.

Bringing history? Import your Strava or Garmin archive, or any FIT file.

Questions

Is it really free?

Yes. Ads pay for the maps and servers. There is no paid tier and nothing to buy.

Do my friends need the app too?

Yes — it is phone to phone. They join by scanning your QR code, with no account. Riders can be up to 200 m apart, and further as phones relay it along the group.

Does it work on Android?

Yes. The map, chat and photos work between any phones running Kardiacs. Group voice works iPhone to iPhone (iPhone 12 or later, iOS 26.4+) and Android to Android (Android 13+ with Wi-Fi Aware).

Does it work with my trainer, watch or bike computer?

Bluetooth FTMS and Wahoo smart trainers, power meters and heart-rate straps pair directly. There is an Apple Watch app. Routes and workouts go out to your bike computer, and the rides it records come back in.

Do I need an account?

No. There is no sign-up wall. Sign in with Google or Apple only when you want your history, routes and gear to follow you between devices and into the web planner.

More questions, answered →