def normalised_achromatic_lightness_correlate(B_r, B_rw):
    """
    Returns the *normalised achromatic Lightness* correlate :math:`L_n^\star`.

    Parameters
    ----------
    B_r : numeric
        *Brightness* correlate :math:`B_r`.
    B_rw : numeric
        Ideal white *brightness* correlate :math:`B_{rw}`.

    Returns
    -------
    numeric
        *Normalised achromatic Lightness* correlate :math:`L_n^\star`.

    Examples
    --------
    >>> B_r = 62.626673467230766
    >>> B_rw = 125.24353925846037
    >>> normalised_achromatic_lightness_correlate(B_r, B_rw)  # noqa  # doctest: +ELLIPSIS
    50.0039154...
    """

    return 100 * (B_r / B_rw)