No comprehensive directory maps everyone's email addresses to their cellphone numbers, but there are often ways to find a mobile number by email ID. You can use online phone directory sites to search, particularly if you know someone's name as well as email address, and you can search on a search engine to try to find a phone number by email address for free. Reverse phone lookup services go the other way, from a cellphone number to other information.
Use a Search Engine
If you have someone's email address but don't know much else about them, you can still try to use that information to track down a cellphone number or other contact information.
One of the most basic ways to this is to use an internet search engine such as Google or Bing. Type in the person's email address, putting it in quotes to search only for exact matches. If the person listed that email address on a business site, online resume or personal homepage, you may be able to find more information about them including a contact phone number.
If one search engine doesn't turn up any results, try another. Additionally, if you can determine the person's name from their email address, such as firstname.lastname@example.org, search for that name on a search engine to see what turns up.
If all else fails, email the person who owns the address and ask for the best contact phone number.
Phone Directory Sites
A variety of online sites provide free phone book listings. Whitepages and ZabaSearch are two well-known directories. They usually require a person's name, not an email address, but if you know the person's name or can discern it from their email address, these directories can be useful tools. Not everyone's phone number is listed in directory sites, and people can have the same name, so tread lightly with how you use numbers from these sites until you make sure that the number you receive belongs to the person you want to contact.
Social Media Searches
Many social media platforms allow you to upload contacts from your phone or email program or search their directories with an email address. This can turn up more information about someone whose email address you have, including cellphone numbers and other contact information. Check the social media platforms you use to see if these options are available.
Reverse Phone Lookup
If you have someone's phone number and want to gather other information, try a Reverse Phone Lookup tool. Reverse directories allow you to enter a phone number and find out who owns it. Two popular reverse phone lookup sites are Anywho and Whitepages. You can also try searching for a phone number on social media or a traditional search engine.