Sages expert in ancient histories have declared that the Purāṇas, according to their various characteristics, can be divided into eighteen major Purāṇas and eighteen secondary Purāṇas.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
एवं लक्षणलक्ष्याणि पुराणानि पुराविदः । मुनयोऽष्टादश प्राहुः क्षुल्लकानि महान्ति च
evaṃ lakṣaṇalakṣyāṇi purāṇāni purāvidaḥ | munayo'ṣṭādaśa prāhuḥ kṣullakāni mahānti ca
SB 12.7.22