how to calculate hash rate of your rig? First going the easy way, I would use any online calculator but most of these mining calculators require the hash rate of my device. I am unable to find a suitable answer or a guide to easily compute this value for any device given its configurations. Will that be possible?

Scenario: 

When I go to these online calculator sites, they again cross question me about the hash rate/ hashing power. I need to determine this value and feed in to these sites so that I can get the desired result. (e.g. cryptocompare.com). I want to know whether it is easy to calculate these values with some information about your machine like the processor, GPUs and all, how much time I am gonna run it. I know the calculator sites need the power input of the device.
This website allows you to select your GPU / ASIC / etc, and it will tell you the expected hashrate of that hardware for different algorithms.

I can offer no guarantees about the validity of the data they provide though, in general the best way to figure out your hashrate would be to actually run the hardware and see what happens.