The above hadeeths indicate that the amount of zakaat ul-fitr is one saa` of the various types of food that can be measured. There is one exception to this: In the case of wheat, the Prophet commanded the people to give two mudds, which are equal to half a saa`1. This was practiced by Mu`aawiyah () in Damascus.
The saa` was a fixed measure of capacity or volume. It varied from one place to another; but the Prophet standardized it by stating:
Weights are according to Makkah's weights; and measures are according to al-MaDeenah's measures.2Thus, the amount should be measured according to al-Madeenah's saa`, which is still available to this time. However, this measure is not accessible to most people. Because of this, many scholars have estimated it approximately to four full handfuls (with the hands put together) of an average man3.
This demonstrates that it is wrong to measure zakaat ul-fitr by weight, because the weight of one saa` varies for different materials. However, if the relationship between weight and capacity is determined for a specific material, the weight of one saa` of that material may then be used.