Treadmill distance way off, calibration making things even worse.

Have you done any outside runs with GPS to help it get your metrics figured out first? I don't know if it makes any difference but it seems like it would be in line with several other Garmin things for it to require GPS running to get it into the right ballpark first.

Take a look at the user manual on Page 2.

When running or walking with GPS turned off, speed, distance, and cadence are calculated using the accelerometer in the device. The accelerometer is self-calibrating. The accuracy of the speed, distance, and cadence data improves after a few outdoor runs or walks using GPS.

The accelerometer will only self-calibrate if it has got something to measure against - ie GPS.

To get better treadmill calibration you need to get some GPS time on the device. Without out that there's no ability for the watch to estimate the distance you cover between arm swings or vertical oscillations. Hence, you cannot expect to get anything reasonable until you've done that.

If running on a treadmill as @philipshanbrok says requires first a run with GPS what is the purpose of having the option to calibrate and save, at the end of a TM run?

Yes, I have logged around 300 km GPS running with the device since mid june, parallell to the treadmill running.

Yes,  I believe there is something broken in the Calibration feature and/or the way treadmill distance is calculated. Would be interesting to hear if anyone is experiencing that treadmill distance as measured by the Fr945 actually is geting more in line with distance recorded by treadmill over time  thanks to calibrating? Would be even more interesting to see Garmin commenting on this..? 

Just found this info from Garmin, confirming that the Calibration feature is indeed suposed to give better distance measurements for future treadmill runs (as you would assume), not just edit the current one. (as stated by a frequent flyer in the 245 forum) 

support.garmin.com/.../

I see happening same with FR945 in last 10 approximately runs in span of three weeks. Running 1 hour on treadmill, and it is adding from 1.50 3 miles often, and once 5.5 miles despite of calibration. I suspect something is wrong based on past experience where in such case, in the second time running it got some how adjusted closer to the actual or realistic miles. (compared to Fennix 3, 5, 5x, 5x plus)

Second issue that I think it is across garmin watches, for integrated application like runkeepr or nike or strava, Garmin or integrated apps read the miles run before calibration. Hence, if garmin count 10 miles for 5 miles run, after calibration to 5 miles, integrated app read 10 miles. This happen with any model of Garmin I've used and not unique to FR945. Anytip? 

I see happening same with FR945 in last 10 approximately runs in span of three weeks. Running 1 hour on treadmill, and it is adding from 1.50 3 miles often, and once 5.5 miles despite of calibration. I suspect something is wrong based on past experience where in such case, in the second time running it got some how adjusted closer to the actual or realistic miles. (compared to Fennix 3, 5, 5x, 5x plus)

Second issue that I think it is across garmin watches, for integrated application like runkeepr or nike or strava, Garmin or integrated apps read the miles run before calibration. Hence, if garmin count 10 miles for 5 miles run, after calibration to 5 miles, integrated app read 10 miles. This happen with any model of Garmin I've used and not unique to FR945. Anytip? 

I think this is how Treadmill Calibration works (or how it is supposed to work).

1. The User initiates a Treadmill run with or without a running pod. The pod accelerometer or the internal watch accelerometer is providing the number os steps (the difference between the two accelerometers is that the accelerometer of the pod is more accurate)

2. The watch is using a certain default initial stride length to calculate the distance. At the end of the race the watch displays a certain distance based on the default stride length and # of steps. For example it tells you have run 7.2K when in fact you ran only 5K. That’s because it’s using a 1.24m stride.

3. You go to Calibrate & Save, and instead of 7.2K you say I ran only 5K. The watch saves this distance, but also based on your corrected input is calculating a new stride length for you.

4. The next time you run on a TM, instead of using the initial default stride length, the watch is supposed to use your specific stride length to calculate the distance, pace, speed, etc. If it’s using your stride length the value for distance will be very close to reality. It will never be perfect but still closer to reality. You can make again other minor adjustments after other runs, but the differences shouldn’t be huge. If this works, the information sent to strava or other tools will be more accurate 

What is is happening in fact with our 245s, 945s is that they are just saving the distance, BUT they are not saving the calibration to take into consideration your own stride length, and to use that in the next runs to calculate the distance 

This is it. It’s so simple.

Having the same issue with my FR945, very frustrating. Been doing the calibration for more than 10 times, result were the same. Never had an issue with my other Fenix & Forerunner watches since 2011. This is one of the major feature for a running watch, Garmin should act fast to fix it.