If your meaning when a website is indexed and appears within the SERP results this can vary from 24hrs to a good few weeks or longer for a site to be fully indexed within Google. There is no definitive answer.
Things you can do to make sure the site is indexed as soon as possible include making sure all on page SEO is fully complete, you have a good internal linking strategy in place, keyword written content and have added a site map and robots .txt file.
Once all that's been done, submitting your site to the search engines also tell them your site is ready to be indexed.
If you make ultra certain and spend the time covering all on page aspects, you have far more chance of the site being indexed, a little work and effort at the front end pays off in the long run.
some of our sites with on page SEO completed fully, within a few days the main pages of the site were showing in SERP results,
how long this takes, depends on the effort you put in.
