Ignoring friction losses, it's proportional to the current. You can easily verify this by applying well-known DC motor
formulas from a text book. If you don't know the I/m constant of your motor, conservation of energy law can you give a rough estimation.
I mean i do have a characteristic curve from the motor, but the current is "only" the Imax current.
This is not the current that i have measured.
Thanks
BR
Vaux