Add the following in “/etc/nginx/nginx.conf”:

location /nginx_status {
        # Turn on stats
        stub_status on;
        access_log   off;
        # only allow access from 192.168.1.5 # Replace with my IP address
        allow 192.168.1.5;
        deny all;
   }

Restart Nginx and now you can visit the status page:

http://nginx_server_url/nginx_status

It will display something like this:

Active connections: 7 
server accepts handled requests
 289626984 289626984 68308182 
Reading: 0 Writing: 1 Waiting: 6 

For example: http://adelaide.sportlogic.net.au/nginx_status

Useful article: https://www.cyberciti.biz/faq/nginx-see-active-connections-connections-per-seconds/