You can always have a look into the list.

Here's the URL: http://academic.research.microsoft.com/RankList?entitytype=3&topDomainID=2&subDomainID=0&last=0&start=1&end=100

The rankings are  based on general reputation of the conference in the field, the citation of the papers published in the conference, reputation of program committee members and reputation of the review process. It is not based on scientific measurements.  While the ranking could change in time. New conferences are typically ranked in the third tier. Top conferences are known for their impact history and their rigorous review process. They should be equivalent, if not superior in impact and prestige, to reputable journals. Workshops and new (or unknown) conferences are not ranked.

In some countries (not all), it is becoming popular this Australian website (http://core.edu.au/index.php/conference-rankings) where conferences are assigned to one of the following categories:

A* - flagship conference, a leading venue in a discipline area

A - excellent conference, and highly respected in a discipline area

B - good conference, and well regarded in a discipline area

C - other ranked conference venues that meet minimum standards

Australasian - A conference for which the audience is primarily Australians and New Zealanders

Unranked - A conference for which no ranking decision has been made

You can search for any word in this URL:

http://portal.core.edu.au/conf-ranks/

For example, if you search for 'communication', you can find something like this:

http://portal.core.edu.au/conf-ranks/?search=communication&by=all&source=CORE2014&sort=arank&page=1

Tier 1 conferences are  which is associated with reputed professional bodies (IEEE, ISTE, IETE)and associations (ACEEE, AEECOM)

Thanks to all for valuable information

Depending on your discipline, you may be able to find an established ranking of conferences.

Search for a ranked conference in the google

https://people.engr.tamu.edu/guofei/sec_conf_stat.htm