Wondering if there is a way to measure the torque of a Stepper motor, I'm working on a application, where it is critical to measure the torque and control the end product output based on the torque.
I infer from that that your purpose for measuring the torque is so that you can control the torque. It is not practical to control the torque of a stepper motor while it is operating. The torque is determined by the limiting current permitted by the stepper motor driver and I am not aware of any driver that allows that to be controlled by an Arduino. It is usually set manually with a potentiometer or DIP switches.
The better stepper motor manufacturers publish graphs that show the torque at different speeds and currents.
And, even if you could reduce the torque the effect would be to cause the motor to miss steps which would completely nullify the value of a stepper motor.
If you have an application where torque-control is important then a regular DC motor will almost certainly be more suitable.
...R