How to adjust the size of a chip in flutter

You can wrap the chip in a Transform widget and scale it as follows:

    Transform(
      transform: new Matrix4.identity()..scale(0.8),
      child: new Chip(
        label: new Text(
          "Chip",
          overflow: TextOverflow.ellipsis,
          style: new TextStyle(color: Colors.white),
        ),
        backgroundColor: const Color(0xFFa3bdc4),
      ),
    ),