Originally Posted by
Brian Elfert
Whatever happened to running out of phone numbers and all the area code splits in the late 1990s? People have more phone numbers than ever now with cell phones, Google Voice, and every other service handing out phone numbers.
Let's look at the number of possible telephone numbers in the US and Canada (North American Numbering Plan).
There are 800 possible area codes. Area codes can't start with 0 or 1 but the other two digits can go from 0 to 9 (8 times 10 times 10 equal 800). Actually, numbers with area codes of 800, 888, 900, etc. are not real numbers and are mapped to real numbers by the network. Just for rough numbers, let's assume 750 possible area codes.
Then you have the exchange number. Can't start with 0 or 1, the second and third digits can't be 11 (x11 not allowed) and 555 (the Hollywood number) is not used. This leaves 791 exchange numbers (8 x 9 x 9 -1 = 791). The subscriber numbers could theoretically go from 0000 to 9999 (10,000 numbers) so the total of subscriber numbers and exchanges are 7,910,000. In reality, some of the numbers are used for special purposes, such as testing in the network, so let's assume 7,500,000.
Multiplying by the 750 area codes gives us 5,625,000,000 (5.625 trillion) phone numbers for the US and Canada (and a few minor areas).
The problem in the past was that a provider was given phone numbers in blocks of 10,000, whether they needed 10,000 or not. Nowdays, the available numbers are put into a pool and when a provider needs a number, it is pulled from the pool.
But there can still be a shortage in an area code (about 7,500,000 in an area code but some are always inactive - given up numbers are not re-issued immediately). That's why you see area code overlays in a large metropolitan area. People, especially a business, do not want to change their existing number so splitting an area code is never a popular alternative.
And just a bit of trivia. Area codes were introduced when we still used rotary phones. So "short dialing" codes were assigned to big cities - 212 to NY and 213 to LA.
Mike
[I just went and looked up the possible area codes. Here are some that are not used:
x11 is not used because if can cause misdialing if the 1 prefix is not used (for example, 911, 411, etc.)
Numbers with the second and third digit the same are not used. So 233 would not be used.
Numbers with 9 in the center, such as 392, are not used because they are used for service codes or reserved
Same for 37x, and 96x - not used because they are used for service codes or reserved.
The toll free numbers are 800, 822, 833, 844, 855, 866, 877, 880, 881, 882, 883, 884, 885, 886, 887, 888, 889. Not all of these are used today. Note that many of these violate the requirements specified above - specifically that the second and third digits not be the same. 890 to 899 are reserved so far.
I haven't tried to figure out how many "valid" area codes that leaves, but it will be less than 750, probably 700 or less, giving us about 5 trillion phone numbers.]
Last edited by Mike Henderson; 07-11-2014 at 11:50 PM.
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