What Is the Rate of Zakat al-Fitr?
Question

What is the rate of Zakat al-Fitr? Is it permissible to give it after the ‘Eid prayer? Is it permissible to give Zakat al-Fitr in cash?
Praise be to Allah.The rate of zakat al-fitr
The Messenger of Allah (peace and blessings of Allah be upon him) enjoined Zakat al-Fitr upon the Muslims at a rate of one sa` of dates or one sa` of barley, and he commanded that it should be given before the people went out to pray – i.e., the ‘Eid prayers. 
In al-Sahihayn, it is narrated that Abu Sa’id al-Khudri (may Allah be pleased with him) said: “At the time of the Messenger of Allah (peace and blessings of Allah be upon him) we used to give Zakat al-Fitr at a rate of one sa` of food, or one sa` of dates, or one sa` of barley, or one sa` of cheese, or one sa` of raisins…” 
A number of scholars interpreted the word food in this hadith as referring to wheat, and others explained it as referring to the staple food of the local people, no matter what it is, whether it is wheat, corn or something else. This is the correct view, because the zakah is a kind of help given by the rich to the poor, and the Muslim should not offer help with anything other than the staple food of his country. 
What must be given is a sa` of all kinds of food, which is four times the amount scooped up with two hands, which is approximately three kilograms. If the Muslim gives a sa` of rice or some other staple food of his country, that is fine. 
When to give to zakat al-fitr
Zakat al-Fitr first becomes due on the night of the twenty-eighth of Ramadan , because the Companions of the Prophet (peace and blessings of Allah be upon him) used to give it one or two days before ‘Eid, and the month lasts twenty-nine or thirty days. 
The latest it may be given is at the ‘Eid prayer, but it is not permissible to delay it until after the prayer, because of the report narrated by Ibn `Abbas (may Allah be pleased with him), that the Prophet (peace and blessings of Allah be upon him) said: “Whoever gives it before the prayer, it is accepted zakah, and whoever gives it after the prayer, it is a kind of charity.” (Abu Dawud) 
Can zakat al-fitr be given in cash?
It is not permissible to pay the value of zakat al-Fitr in money , according to the majority of scholars, and the evidence for this view is more sound. Rather it should be given in the form of food, as was done by the Prophet (peace and blessings of Allah be upon him), his Companions (may Allah be pleased with them) and the majority of the ummah. 
We ask Allah to help us and all the Muslims to understand His religion and adhere steadfastly to it. May Allah bless our Prophet Muhammad and his family and Companions. 
For more, see this article: All About Zakat al-Fitr
And Allah knows best.