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Split a FIT File
Break one long FIT recording into separate, upload-ready activities. Split by distance or time, and each part comes out as a complete FIT file — its own session, its own laps, summary numbers recomputed from the records inside it. All decoding and cutting happens locally in your browser.
or click to browse — output will be FIT; format detected automatically
How to split a FIT file
- 1
Drop the file
Drag the .fit file onto the box above. It is decoded locally in a background worker, and the full track appears on the map with its stats.
- 2
Choose the split
Pick distance or time and set the segment length. The tool shows how many parts the recording divides into before you commit.
- 3
Preview the parts
Each part is listed with its own distance, duration and ascent, and the cut points are marked on the map — check that the boundaries land where the stages actually break.
- 4
Download the parts
Save the segments; each is a complete, valid .fit ready to upload as its own activity. The original file is never modified.
Why split a FIT file?
The all-day recording is the classic case: the computer kept running through every coffee stop, or you simply forgot to stop it, and now one .fit file claims a single monstrous activity — wrong distance, wrong start time, one distorted map. Splitting the recording back into the rides, runs or hikes that actually happened makes it honest and uploadable again.
Distance is the other trigger. Tour-length recordings — a multi-day bikepacking leg, a brevet, an ultra — strain platform upload limits, render sluggishly and bury the interesting parts in hours of coastline. Cut into stages, each piece uploads as its own activity, shares cleanly and stays responsive in analysis tools.
How FIT splitting works
Like merging, splitting respects the FIT file's structure. The record stream — the GPS, heart rate and power samples — is cut at real record boundaries: when your distance or time threshold is crossed, one part ends at the last record before it and the next begins with the following record. No records are interpolated, averaged or invented.
Each part is then rebuilt as a standalone FIT activity: its own file_id, its own session, and the laps that fall inside it preserved in order. Session summaries — distance, elapsed time, ascent — are recomputed from the records each part actually contains, so every file's numbers describe itself, not a scaled fraction of the original.
Honest caveat: FIT's optional extras, such as developer-defined data fields, may not survive the re-encoding into new files. The core training data — position, time, altitude, heart rate, cadence, power — always does.
When a desktop tool is the better answer
Time-gap splitting is a blunt instrument for one special case: a file that strings several different sports together. Cutting at the pauses usually separates them fine, but if activities overlap or the structure is messy — a triathlon file, say — a desktop tool like GoldenCheetah gives you the precision to separate activities by lap and session properly.
And a splitter is the wrong tool for broken files: a truncated or corrupt .fit fails to decode with a clear error, as it should. Repair FIT File is the free tool for that job. For everything that is simply too long, splitting is the quick, honest fix.
Your files never leave this browser
This tool — like every tool on this site — runs entirely as client-side JavaScript. The file you drop is parsed in a Web Worker on your own device, converted in memory and handed straight back to you as a download. There is no upload endpoint, no server-side conversion service and no temporary storage: you can watch the network tab in your browser's developer tools and confirm that no file bytes are transmitted anywhere.
That matters more with fitness data than with most files. A GPS track is a precise log of where you were, at what time, and how hard your heart was working — home address, training habits, favorite routes and race schedule all in one file. Keeping conversion on-device means third-party converters never get a copy of that log, and the tool keeps working identically on a plane, in a basement, or anywhere else without signal.
Frequently asked questions
Yes. Every part is a standalone FIT file with its own file_id and session, so Garmin Connect, Strava and training platforms treat it as an independent activity with its own date, distance and summary.