Kaval Chandrayana Vrat (Kāval/Kaavali Chandrāyana) is a traditional Jain tapa (penance) in which the quantity of food is regulated by counting mouthfuls (kaval/kavali = morsels) in harmony with the lunar fortnight. It is meant to subdue rasa-asakti (attachment to taste), strengthen samyama (self‑restraint), and purify kashāyas (anger, pride, deceit, greed).

What “kaval” means

• One kaval is one mouthful/morsel for that individual. The size is natural to the person; it is not artificially enlarged.
• Water is taken as per your guru’s guidance (boiled/filtered, within allowed time).

Main types

• Shukla Chandrayana: begin on the first day of the bright fortnight (Shukla Paksha) with 1 kaval; increase by 1 each day up to 15 kavals on Purnima.
• Krishna Chandrayana: begin on the first day of the dark fortnight (Krishna Paksha) with 15 kavals; decrease by 1 each day down to 1 kaval on Amavasya.
• Full Chandrayana cycle (observed by some): do Shukla (1→15) followed immediately by Krishna (15→1). Many laypeople take only one fortnight as a vowed penance.

Basic way to observe (simple, safe outline for a shravak/shravika, under guidance) 1) Purva-vidhi: Do alochanā-pratikraman, take pratyākhyān (formal resolve) from your guru/pravartak. State which type (Shukla or Krishna), start date, daily kaval count, and parihār‑viśuddhi (what you will do if you falter). 2) Daily food discipline: - Eat only once in the day, before sunset, observing apramattatā (carefulness). - Count exact kavals for that day’s number. Keep the plate simple; avoid taste‑enhancers. - Maintain samiti and guptis: gentle movement, careful speech, and mental vigilance. 3) Daily sādhana: - Devotional recitation, pratikraman, kayotsarga, and svādhyāy as per capacity. 4) Parihar: If a lapse occurs (e.g., extra morsels), confess the fault (ālochana), accept the small expiation fixed in your resolve, and resume correctly.

Important notes and variations

• Digambar and Śvetāmbara both recognize Chandrāyana as a kaval‑based tapa. Details vary by lineage (e.g., exact start day, rules for water/milk, whether āyambil is coupled on very low‑kaval days, and how to measure a kaval). Always follow the maryādā set by your own guru/tradition.
• Health: Not advised for children, pregnancy, the elderly without strength, or anyone ill. Begin only with guidance. If weakness arises, stop respectfully and report to your guru.
• Conduct: Non‑violence and truthfulness are primary. Food must be pure Jain āhār, taken with vigilance, without night‑eating.

Spiritual intent (artha)

• The vrat aligns the mind with the steady rhythm of vrata and the moon’s cycle, loosening attachment to taste and quantity. It cultivates inner equanimity, carefulness, and devotion, supporting right conduct and aiding in the shedding of karma.

If you need step‑by‑step day counts, sample pratyākhyān wording, or eligibility checks specific to your tradition, please refer to your guru or your sangh’s published maryādā and follow that exactly.