I have an UIImageView that is a subview of an UIView. I'm trying to create a drag rotate effect with the UIImageView similar to spinning a bottle but I'm having trouble calculating the radians to rotate the image by. My code below seems like it should work because I've seen a similar calculation in Flash examples. Can anyone shed some light on what I'm doing wrong? Thanks. This is the code contained in my image view subclass: - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { UITouch *touch = [[event allTouches] anyObject]; lastLocation = [touch locationInView:[self superview]]; } - (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event { UITouch *touch = [[event allTouches] anyObject]; CGPoint location = [touch locationInView:[self superview]]; CGFloat xDisplacement = location.x - lastLocation.x; CGFloat yDisplacement = location.y - lastLocation.y; CGFloat rad = atan2f(yDisplacement,xDisplacement); self.transform = CGAffineTransformMakeRotation(rad); }