def preboil_grav(target_og: float,
                 preboil_vol: float = 7,
                 postboil_vol: float = 6):
    """Computes preboil gravity to to verify before concluding mash

    Args:
    preboil_vol: Pre-boil volume in gal
    target_og: Target original gravity for primary fermentation e.g. 1.040
    postboil_vol: Postboil wort volume to be collected for primary fermentation
    """
    target_og = (target_og - 1.0) * 1000  # adjust to gravity points
    return (((postboil_vol * target_og) / preboil_vol)/1000) + 1.0