A great kalpa (Skt. mahākalpa; Tib. བསྐལ་ཆེན་, kalchen, Wyl. bskal chen) is the period of time during which a universe passes through the four periods of

1. formation (Tib. ཆགས་པའི་བསྐལ་པ་, Wyl. chags pa'i bskal pa),
2. duration (Tib. གནས་པའི་བསྐལ་པ་, Wyl. gnas pa'i bskal pa),
3. destruction (Tib. འཇིག་པའི་བསྐལ་པ་, Wyl. 'jig pa'i bskal pa) and
4. voidness (Tib. སྟོང་པའི་བསྐལ་པ་, Wyl. stong pa'i bskal pa).

These four periods can be referred to as intermediary kalpas. Generally, a great kalpa is composed of eighty intermediary kalpas, twenty for each of these four periods.<ref>For more details see Kangyur Rinpoche, Treasury of Precious Qualities (Boston & London: Shambhala, 2001), 'Appendix I'.</ref>

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