How do I know when I'm using the right number of keywords on a page ?

Hi Friends,
There is one term which is used for keyword optimization i.e Keyword density

KD= no. of times keyword used on page/no. of words on page x 100

Safe and recommended keyword density is 2–4%

Using more than 5% keyword density is dangerous for Google SEO.

You can use these tools for analyzing keywords like

• Google search console
• 
  SEO quake
• 
  MOZ toolbar
• 
  SEO Yoast Plugin