Merge FIT Files from Two Devices

Recorded the same session on a watch and a bike computer? Copy heart rate, power, cadence, GPS or altitude from one file into the other, so one upload has the best of both.

Lining the files up

Two devices rarely agree on the time. The tool matches the files using speed, heart rate or power and lines them up automatically. A chart shows both traces on top of each other, with a slider to nudge the second file by a few seconds before you merge.

What to copy

The main file keeps its GPS, laps and summary unless you choose otherwise. Tick the data to copy from the second file, and averages and maximums are recalculated.

Quick answers

Why merge FIT files?
A common case is a bike computer with good GPS and power, and a watch with the heart rate. Merging gives one activity with all of it, so your training load is right.


What if the clocks were minutes apart?
The tool searches up to ten minutes either way to find the best match. Check the chart, adjust the slider if needed, then merge.

More free tools for your activity files are on the FIT file tools page.


Small things I always use

Watches and sensors

On the bike

Home and indoor training

  • NPE Runn: Makes my basic treadmill smart, sending more accurate speed and distance to my watch and Zwift. I use it.
  • Google Wifi: Keeps Zwift connected in my pain cave. I use it.
  • Apple TV 4K: Zwift on the big screen. I use two.
  • Google Nest Doorbell (wired, 2nd gen): My video doorbell, running in both Google Home and Apple Home. I use it.

Health, recovery and sleep

  • FreeStyle Libre 3 Plus: Shows how my blood sugar responds to diet.
  • hDrop: Measures my sweat loss in summer and indoors.
  • Fourth Frontier Zone: Checks my heart under load in hard sessions.
  • Kineon MOVE+: Red and infrared light for sore knees, Achilles and other joints after hard training. I use it.
  • Oura Ring 5: My partner’s recovery tracker of choice.
  • Eight Sleep: A cooling mattress cover my partner and I use nightly.


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