Fidyah is compensation paid instead of fasting, for a fast a person is unlikely ever to be able to make up. The Quran states that those who can only fast with great difficulty have the option of feeding a needy person for each day missed (2:184). In practice, jurists apply this to the elderly and to those with a chronic illness with no realistic hope of recovery — people for whom qada is not a future option. Some scholars also extend it to a pregnant or breastfeeding woman who fears for her child's health, either instead of or alongside qada, though this is debated. As for the amount, the classical measure is one mudd (roughly 600–750 grams) of a staple food, or its cooked equivalent, per missed day — enough to provide one person a full meal. Many local scholars and fiqh councils today convert this into a cash value based on the average cost of a meal, multiplied by the number of days missed. It can be paid to one poor person for all the days at once, or distributed among several, and there is no requirement to wait until Ramadan ends to begin paying it.
Q&A · Fasting
Who is required to pay fidyah instead of fasting, and how much is it?
References
Informational, not a personal fatwa. Consult a qualified scholar for rulings on your situation.