from typing import List


def ordered_list_item_to_percentage(ordered_list: List[str], item: str) -> int:
    """Determine the percentage of an item in an ordered list.

    When using this utility for fan speeds, do not include "off"

    Given the list: ["low", "medium", "high", "very_high"], this
    function will return the following when when the item is passed
    in:

        low: 25
        medium: 50
        high: 75
        very_high: 100

    """
    if item not in ordered_list:
        raise ValueError

    list_len = len(ordered_list)
    list_position = ordered_list.index(item) + 1
    return (list_position * 100) // list_len