I'm working on a Digital Wattmeter project, where the wattmeter is plugged to the mains, and an appliance is plugged to the wattmeter.

My question is, is there a way to measure Power Factor accurately?

EDIT:
I have heard of a Power Factor IC, which conveniently measures the power factor when connected. However, I could not seem to come across it.

 

If you have an oscilloscope you can find the phase difference between the voltage and current and thus the power factor.

 

I might have access to an oscilloscope, however, since I am building a wattmeter, I cannot use the oscilloscope to measure power factor.

Is there an alternative?