What is the height of iPad's onscreen keyboard?

The portrait height is 264 while the landscape height is 352.

I know this is a late answer, but I just came across this question myself.

- (void) keyboardWasShown:(NSNotification *)nsNotification {
    NSDictionary *userInfo = [nsNotification userInfo];
    CGSize kbSize = [[userInfo objectForKey:UIKeyboardFrameBeginUserInfoKey] CGRectValue].size;

    NSLog(@"Height: %f Width: %f", kbSize.height, kbSize.width);
    // Portrait:    Height: 264.000000  Width: 768.000000
    // Landscape:   Height: 352.000000  Width: 1024.000000
}

The answer is: it depends.

I am aware of 16 different heights the keyboard can be, and it can be in any position.

It is different for:

1. landscape/portrait,
2. webview/non-webview,
3. asian character selection style, regular language
4. split keyboard / non-split

I have attached an image showing some different possible configurations.

Rather than enumerating all 16 possibilities, I think you want to observe UIKeyboardWillShowNotification/UIKeyboardWillHideNotification and UIKeyboardDidChangeFrameNotification (iOS 5.0+), and then get the keyboard's frame from those events.