The way Sadaqah al Fitr is calculated and paid differs from that of Zakat

For example:

One doesn't  Zakat eligible items such as cash, gold, silver, etc.. in his possession, but he has other assets equal to the value of Nisab in excess of his personal and basic needs, such as having a surplus car computers, furniture,eating utensils etc… In this case, although Zakat will not be obligatory, but one  will have to pay Sadaqa al-Fitr. The amount that needs to be paid for Sadaqa al-Fitr is half Sa’ of wheat or one Sa’ of barley or dates. According to todays' standards  one Sa' is  equal to 3.2 kilograms or approximately 7.0 pounds (7.05479239 lbs to be precise).

It is permissible to pay the value of these in cash. It is preferable to give cash when the above items such as wheat, barley, date, etc… are easily available. When these items are scarce, then it is better to give them instead of cash.  The value of the items are according to the value in the local market where one resides. Hence the value of 3.5 pounds of Wheat, or the value of 7.0 pounds of dates, raisins or barley can be donated per person.