How much location information can you get from cell phone caller ID?

http://en.wikipedia.org/wiki/Caller_ID#OperationNumber-only caller ID is called Single Data Message Format (SDMF), which provides the caller's telephone number, the date and time of the call. Name+number caller ID is called Multiple Data Message Format (MDMF), which in addition to the information provided by SDMF format, can also provide the directory listed name for the particular number. Caller ID readers which are compatible with MDMF can also read the simpler SDMF format, but an SDMF caller ID reader will not recognize an MDMF data stream, and will act as if there is no caller ID information present, e.g. as if the line is not equipped for caller ID.So any phone that tells you the user's location is likely* telling you the location for the area code, which is nearly meaningless in this era of people traveling around the US with the same cell phone number. You can always http://www.fcc.gov/guides/caller-id-and-spoofing, or illegally http://en.wikipedia.org/wiki/Caller_ID_spoofing (Wikipedia page with no direct links to such services). If you don't need to use your own cell phone, http://www.wikihow.com/Block-Caller-ID.

It is based on the area code (at least it was two years ago, as per my next paragraph): I live in Minneapolis. My co-worker also lives here in Minneapolis, but his phone number was assigned to him while he lived in Missouri, and thus has a Missouri area code. Whenever he would call me before I put him into my contacts, it would always say Missouri on my caller ID even though he was physically living in and calling from Minneapolis.

Same as TinWhistle -- my cell phone has an 865 area code (Knoxville, Tennessee), but I live in suburban Detroit. When I call people, it shows up as coming from Knoxville.

Your cell phone carrier may have a way to block your caller ID information from showing up at all, or there may be an option in the settings on your phone to block caller ID, but instructions and options are very dependent on your phone and your carrier.

Building off of Filthy Light Thief; one can block caller-id, but be aware that if you're calling a toll free number, http://en.wikipedia.org/wiki/Automatic_number_identification makes your number available. I'm not sure, but ANI also might allow your cell number to show up on the bill - as you're the originator, and the receiver doesn't handle tolling I suspect not. But it definitely won't include GPS coordinates, receiving cell tower coordinates, or similar. You have more to fear of social media linking your location than Caller ID.

Just to add to the anecdata: my boss has a cell phone with an area code number from his previous residence, in Ohio. Anytime he calls me or I call him, whether we're both here in Virginia or sometimes when I'm in Virginia and he's over in DC, his location always shows as Ohio. Ditto the time I had to call when he was on vacation in Florida: the phone company still said he was in Ohio.

illegally http://en.wikipedia.org/wiki/Caller_ID_spoofing (Wikipedia page with no direct links to such services) Also, non-illegally, simply using a prepaid calling card—the sort that involves calling into a toll-free access number first and then entering a PIN and a destination number—may cause the caller ID information that shows up to be from whatever outgoing line you happen to be connected through. You could call yourself first to see what it looks like, though I suppose it's not necessarily guaranteed to be the same every time. (Theoretically the card company's computer system could forward your original caller ID info, but I haven't run across this myself.) (And of course like other caveats above, the police or the NSA or whoever would still be able to figure out where a call came from.)