def recipe_srm(recipe):
    """Return a recipe's SRM"""
    if 'fermentables' not in recipe:
        return '0'
    mcu = 0
    for f in recipe['fermentables']:
        mcu += float(f['amount']) * float(f['color']) / float(recipe['volume'])
    return '{:.0f}'.format(1.4922 * mcu ** 0.6859)
