While I was designing Icons for my client, I realised that it is true in website design as it is in Icon Design: you can work in odd numbers,
When you have even numbers like 14px Square or 16px Square, you can easily fit a round box inside it, but in a 15px Square Icon, it’s tough to manage…
Here is The example…
Odd Numbers of Pixels:
Odd Pixels with 15px by 15px
Even Numbers of Pixels:
10px by 10px, with 1px of rounded corners, it fails to generate an illusion of circular when viewed at actual size or maximum size
16px by 16px, with 1px of rounded corners, it fails to generate an illusion of circular when viewed at actual size or maximum size
20px by 20px, With 20px by 20px with a radius of more than 3 pixels, it creates perfectly rounded corners for squares or rectangles & it does create an illusion of circular when viewed at the actual size
You must have a minimum of ‘3 Pixels’ of Round Curve to look refined, finished & crisp on screen.
It is just my experience. I hope it helps you too…
Thanks & Regards
Mandar Apte