Workout file converter — FIT, TCX, ZWO & Garmin
Convert workout files between FIT, TCX, ZWO (Zwift), and Garmin Connect formats — free, in your browser, with no account and no file upload. Drop a file into the Kaiord Editor and download the result. Developers can script the same conversions with the CLI or the TypeScript SDK.
Every conversion goes through KRD, Kaiord's canonical format, so round-trips stay within tight tolerances (time ±1 s, power ±1 W or ±1 % FTP, heart rate ±1 bpm, cadence ±1 rpm). See the KRD format for the details.
Pick a conversion
| From ↓ / To → | FIT | TCX | ZWO (Zwift) | Garmin |
|---|---|---|---|---|
| FIT | — | FIT → TCX | FIT → ZWO | FIT → Garmin |
| TCX | TCX → FIT | — | TCX → ZWO | TCX → Garmin |
| ZWO | ZWO → FIT | ZWO → TCX | — | ZWO → Garmin |
| Garmin | Garmin → FIT | Garmin → TCX | Garmin → ZWO | — |
All twelve directed pairs have a guided walkthrough. Every conversion uses the same kaiord convert command and SDK calls — the format is detected from the file extension.
Three ways to convert
- Editor — kaiord.com/editor. Drag & drop a file, pick the target format, download. Nothing leaves your browser.
- CLI —
kaiord convert -i workout.fit -o workout.zwo. Formats are detected from the extensions. See the CLI reference. - SDK —
@kaiord/coreplus the reader/writer for each format. See the Quick Start.
What is lossless?
KRD is designed to be round-trip safe, but the source and target formats are not identical — each pair page has a "What survives the conversion" table and the gotchas that matter for that direction. In short:
- FIT is the richest workout format (power, heart rate, cadence, speed, and distance/time durations).
- TCX workout targets are heart rate, speed, and cadence — not power.
- ZWO is power-based (% of FTP); heart-rate and cadence targets have no native equivalent.
- Garmin Connect (GCN) covers power, heart rate, speed, and cadence in watts/bpm/rpm, plus calorie durations.
Format-specific data that has no target-side equivalent is preserved under the KRD extensions object so it can survive a later round-trip.