How to Merge Two Garmin Activities Into One

It happens a few times a season. The battery dies 4 km from home, the device auto-saves during a long coffee stop, or a crash reboots the computer mid-climb — and one ride becomes two half-rides. Your weekly totals are wrong, the map has a hole in it, and the milestone you actually rode is split across two entries.

Neither Garmin Connect nor Strava can merge uploaded activities. The fix is done at the file level: take the two original FIT files, combine them into one valid activity, upload that, and delete the halves.

Step 1: Get both originals

In Garmin Connect (web), open each half, use the gear menu, and export the original FIT files. If the device still holds the recordings, exporting fresh copies is fine too. Name them so the order is obvious — the timestamps will confirm it, but life is easier when the filenames already say it.

Sanity-check the halves: both should be FIT files from the same device, and the second should start after the first ends. That last condition is what separates a merge from a mess — more on that below.

Step 2: Merge them

Use the FIT merge tool. Drop both files in; the merge runs entirely in your browser — the files never leave your device — and produces one FIT activity built the way a device would have written it:

• One session, ordered by the earliest start time, so the result reads as one chronological activity.
• Records in timestamp order, first half then second, as if the recording had never stopped.
• Laps preserved as consecutive laps of that single session — an interval structure from either half survives intact.
• Session summaries recomputed from the combined records. Distance, time and ascent match what the merged file actually contains, rather than the stale per-half numbers.

The gap between the recordings — the coffee stop, the walk home after the battery died — is preserved honestly as elapsed time. A merged activity is a truthful record of two segments, not an invention of a continuous one.

Step 3: Upload the result

Upload the merged file as a new activity, then delete the two halves. Deleting after the upload succeeds matters: platforms de-duplicate against existing activities, and two activities with the same start time can make the upload look like it silently failed (why that happens).

When merging is the wrong fix

The tool is honest about its limits, so this guide is too:

• Simultaneous recordings. Two devices on the same ride (your watch and your head unit) produce overlapping timestamps. A merge interleaves both point streams, and distance comes out longer than reality. Pick the better recording; archive the other. Merging is for sequential files.
• Different sports or different days. A Tuesday run and a Sunday ride merged into one session produce a nonsense summary spanning everything in between. If you want a combined total, that is a reporting question, not a file question.
• Badly damaged files. If either half is truncated or corrupt, merge after repair — run the file through FIT repair first, or the merge inherits the damage.
• Byte-level fidelity. Developer-defined data fields and exotic message types may not survive re-encoding. GoldenCheetah or vendor tooling is the rigorous route when every field must be preserved.

The GPX variant

Same situation, different destination: if the halves are GPX tracks headed for a map or route planner rather than a training platform, merge the GPX files instead — tracks concatenate, no session structures involved, and the result stays a plain GPX.

The whole recipe in one line

Export both FITs → merge → upload → delete the halves. Five minutes, and the ride reads the way you actually rode it.