The Zakat al-Fitr is essentially charity during the blessed days of Ramadan so that purification from idle and indecent activities is achieved during fasting, along with providing for the needs of the poor and destitute on the occasion of Eid, and also expressing gratitude for the blessings obtained through fasting.
The thing is that the amount of Zakat al-Fitrah is determined based on the value of one saa' of food. A saa' is an ancient measurement unit used during the time of the Prophet Muhammad ﷺ, and its equivalent in modern measurements may vary depending on the region.
Each eligible person in the household, including dependents, must pay Zakat al-Fitr. The head of the household calculates the total amount owed by multiplying the value of one saa' by the number of eligible individuals.