def colourBarMinorAxisSize(fontSize):
    """Calculates a good size for the minor axis of a colour bar.

    The minor axis is the axis perpendicular to the colour bar axis.

    :arg fontSize: Font size of colour bar labels, in points.
    """
    fontSize = fontSize
    fontSize = 6 + 96 * fontSize / 72.0
    return round(2 * fontSize + 40)
