What is not exact about it?
Unless the treadmill is calibrated you don't really know what speed the belt is going at..
Ah. That would be a pretty major design flaw if it was very off. I might do some experiments...
The accuracy is apparently not that good normally. Check out the DC Rainmaker review and a sensor that can check it. https://www.dcrainmaker.com/2020/01/npe-runn-tread...
I now have images of Murray taking his trundle wheel to the gym before a session.
Igor - I'd seen that and it looks pretty tempting. Might go old fashioned with stopwatch/tape on the belt first though.
I'm happy believing I'm running the speed the treadmill says I am. I do usually try to run on the same machine each time so at least it won't change much week to week.