Emulator in Android Studio doesn't start

I had the same problem. I just created the AVD with 768 MB RAM and it did run fine!

I had a similar problem... Android Emulator doesn't open. You need to discover the reason of this... You could run your emulator from the command line. For this you could copy and paste your command line from "Run" or "AVD" Android Studio console. For example:

"{path}\android-sdk\tools\emulator.exe -avd Default_Nexus_5 -netspeed full -netdelay none"

When you launch it from a command line terminal, It give you a message with the error. In my case it was useful for discover the problem:

..\android-sdk\tools>emulator: ERROR: x86 emulation currently requires hardware acceleration! Please ensure Intel HAXM is properly installed and usable. CPU acceleration status: HAX kernel module is not installed!

• I needed to activate GPU acceleration with a tool to enable it on my machine. I solved it installing from SDK Manager the tool HAXM...

• I had another problem... For example i had assigned a bad url for skin path of my virtual device... To solve it I have configured my virtual device with a valid skin from my platform sdk: '{path}\android-sdk\platforms\android-{number}\skins{SCREEN_SIZE}'

Now it is opening fine.

Update 8/8/2019:

For newer version of Android SDK, emulator path should be:

"{path}\android-sdk\emulator\emulator.exe"

reference (thank you @CoolMind)

In my case the android hangs at start up. I solved by wiping user data and forcing a cold boot, using Android Virtual Device Manager (Tools->AVD Manager)