def massCharge(predictedMass, z):
    """
    Called by chargeIonMass() this function calculates the m/z ratio which corresponds to the input monoisotopic mass
    and charge state.

    :param predictedMass: the monoisotopic mass which is to be converted to an m/z ratio.
    :param z: an integer representing the charge state, where i corresponds to +i.

    :return chargeMass: the calculated m/z ratio.
    """
    chargeMass = (predictedMass + (z * 1.00794))/z
    return chargeMass