The following steps show how to locate your computer's IP Address:

Windows

• Click Start, and then select All Programs.
• Click Accessories, and then Command Prompt. (or simply click Start and then write command prompt in the run or search programs and files box)
• At the command prompt, enter:  ipconfig
• The IP address (or IPv4 address, if you are using Windows 7 or Vista) will be a series of numbers following the pattern xxx.xxx.xxx.xxx (i.e., 156.56.27.32).

Mac OS X

OS X 10.6 or 10.5

• From the Apple menu, select System Preferences.
• In System Preferences, from the View menu, select Network. 
• In the Network preference window, click a network port (e.g., Ethernet, AirPort, modem).
• You'll see its IP address under "Status:"

OS X 10.4 or 10.3

From the Apple menu, select Location, and then Network Preferences. 

In the Network Preference window, next to "Show", select Network Status.

Via the web

If you are connected to the Internet, visit WhatIsMyIP.com. The site will display your IP address and other information about your system. 

Note: A public IP also referred to as external IP is shown on IP locator websites. If your computer connects to a router then the computer will most likely get an internal IP address like 192.168.1.100 and your router will get the external IP address.