Number of users supported by Standard 4GB and 8GB plan

I have been using Linode for quite some time, I began hosting my site using the 4GB, 2CPU, 80GB storage and 4GB Ram Standard plan. The max visitors it could support was 900 visitors at a time. The stat is obtained from Google analytics.

Beyond 900 the CPU usage is 100% and my site starts loading slowly, let's just say the performance becomes horrible.

So I moved to 8GB, 4CPU, 160GB storage, 8GB Ram Standard plan. Now the CPU is 4 rather than 2, so doing the math I thought the maximum visitors it could carry at any time is 1800, but I am wrong!

The maximum visitors my site could run smoothly before CPU gets to 100% or "504 gateway error" starts showing up is just 1400.

Now, I am definitely getting a bigger plan!!

I want to know the stats if anyone else is willing to share, I might need to tune the settings further for more optimization.

Thank you