Convert FIT to Garmin

Scope

Converts structured workouts (steps and targets), not recorded activities. See Workouts vs. activities.

Turn a Garmin FIT workout into the Garmin Connect workout format (GCN JSON) so a session from a FIT file can live in your Garmin Connect account and sync to your watch or head unit. Use the free, in-browser Kaiord Editor (no account, no upload), or the CLI and TypeScript SDK. Conversions go through Kaiord's canonical KRD format and stay within round-trip tolerances (time ±1 s, power ±1 W, heart rate ±1 bpm, cadence ±1 rpm).

Three ways to convert

1. Editor (in the browser)

Open kaiord.com/app, choose your .fit file (GCN is already selected as the export format), and download the result. To send it straight to your account, use the Editor's Garmin sync (backed by the garmin-bridge extension).

2. CLI

Pass your FTP in watts with --ftp when the workout has % FTP targets:

pnpm add -g @kaiord/cli
kaiord convert -i workout.fit -o workout.gcn --ftp 250

To push directly to Garmin Connect (after kaiord garmin login):

kaiord garmin push -i workout.fit --input-format fit --ftp 250

3. SDK

import { fromBinary, toText } from "@kaiord/core";
import { fitReader } from "@kaiord/fit";
import { createGarminWriter } from "@kaiord/garmin";
import { readFile, writeFile } from "node:fs/promises";

const buffer = await readFile("workout.fit");
const krd = await fromBinary(new Uint8Array(buffer), fitReader);
const gcn = await toText(krd, createGarminWriter({ ftpWatts: 250 }));
await writeFile("workout.gcn", gcn);

What survives the conversion

Data	FIT	Garmin Connect (GCN)	Result
Step order & names	workout steps	workout steps	Preserved
Time durations	seconds	time durations	Preserved (±1 s)
Distance durations	meters	distance durations	Preserved
Power targets	watts / zone	watts / power zone	Preserved (±1 W; zones map across)
% FTP power targets	% FTP / range	watts / watt range	Converted using your FTP (see below)
Heart-rate targets	bpm / zone	bpm / heart-rate zone	Preserved (±1 bpm)
Cadence targets	rpm	rpm	Preserved (±1 rpm)
Speed / pace targets	m/s	m/s	Preserved
Repeats / intervals	repeat steps	repeat blocks	Preserved
Developer fields	custom fields	—	Preserved under extensions.fit

FIT and Garmin Connect are both Garmin-native formats, so this is one of the highest-fidelity conversions Kaiord does.

Gotchas

% FTP power targets need your FTP. A FIT workout can store power as % FTP, but Garmin Connect workouts store watts, so those targets — single values and % FTP ranges alike — are converted with your FTP (watts = round(% / 100 × FTP)). Set your FTP in Athlete in the Editor, or pass --ftp <watts> to kaiord convert / kaiord garmin push. Without one the conversion stops with an error rather than guessing.

FIT file vs. Garmin Connect JSON. A .fit file is Garmin's on-device binary format; a .gcn file is Garmin Connect's workout JSON. They are not the same thing, which is why the conversion matters — the GCN output is what the Garmin Connect API accepts.

How does it get on my watch? Push the .gcn to your account with kaiord garmin push (via @kaiord/garmin-connect) or use the Editor's Garmin sync; Garmin Connect then syncs it to your device.

Developer and unknown fields. FIT developer fields and unknown messages have no Garmin Connect equivalent, so they are kept under extensions.fit and survive a later garmin-to-fit round-trip rather than being emitted into the GCN workout.

Related

• Convert Garmin to FIT — the reverse direction
• Convert FIT to TCX — a cross-platform FIT export
• FIT format · GCN format
• All converters