In Jainism, "upvas" (also spelled upvaas or upavas) refers to fasting, specifically abstaining from food for a set period as a form of spiritual practice and self-discipline.

There is no fixed number of upvas that one must do in Jainism; it depends on an individual's capacity, spiritual inclination, and vows. However, traditionally, many Jains observe upvas on the following occasions:

1. Pakkhi Upvas: Fasting twice in a lunar fortnight (on the 8th and 14th day of each fortnight), totaling four times in a lunar month.
2. Aayambil Oli: Fasting or taking a special restrictive meal (aayambil) for 9 days, twice a year.
3. Paryushan Parva: Many observe upvas during the 8-10 days of Paryushan.
4. Masakshaman: Some Jains take up the vow of fasting on specific days every month.

There are also various types of fasting (tapas) in Jainism, such as:

• Upvas: Complete abstinence from food and sometimes water for 24 hours.
• Ekashana: Eating only one meal a day.
• Biyasana: Eating two meals a day, with restrictions.
• Aayambil: Eating only one type of bland food once a day.

Some devout Jains may undertake upvas as frequently as possible, while others may do so on special religious days or festivals. In summary, the number of upvas is not fixed in Jainism and is based on an individual’s vows, ability, and devotion.