Is there a way to meassure motor KV?

According to the Electric Skateboard Calculator the final speed on my Vanguard build on @Torqueboards 190KV motors is spot on, extremely precise, but on my Reaper with 190KV motors from Polar my speed is off by 5km/hr.

I wonder if there is a way to meassure KV directly on the motors to see if Polar motors are in fact 170KV or 190KV as I thought from the begining.

Loaded Vanguard

Never Summer Reaper

If I change the motor to 170KV the speed matches the skateboard calculator perfectly.

The motor constant (Kv) is measured without a load. There are expected losses in power.

Both speeds were meassured on the bench, so both e-boards are subjected to the same loses, however the Vanguard matched the speed and the Reaper not.

In the bldc tool, after you have ran the motor, go in the terminal and type “kv”

You will get the kv in erpm, divide that number by 7