It is not certain how he turned his small ancestral kingdom into an empire, although a widely accepted theory among modern historians is that his marriage to the Licchavi princess Kumaradevi helped him extend his political power.

[11] Some historians, such as D. C. Sircar and R. C. Majumdar, theorize that the Gupta era marks the coronation of his son Samudragupta.

[12] S. R. Goyal theorizes that the era was started by the later king Chandragupta II, but its beginning was dated to Samudragupta's ascension.

[9] Chandragupta I probably had a long reign, as the Allahabad Pillar inscription suggests that he appointed his son as his successor, presumably after reaching an old age.

[16] An 8th-century inscription of the Lichchhavi dynasty of Nepal claims that their legendary ancestor Supushpa was born in the royal family of Pushpapura, that is, Pataliputra in Magadha.

Therefore, the claim made in this inscription, even if true, cannot be taken as concrete evidence of the Lichchhavi rule at Pataliputra during Chandragupta's time.

Given the lack of any other evidence, historian R. C. Majumdar assumed that during Chandragupta's time, the Lichchhavis ruled at Vaishali, which is the only other base of the clan known from the historical records.

[7] Numismatist John Allan theorized that Chandragupta defeated a Lichchhavi kingdom headquartered at Vaishali, and that Kumaradevi's marriage to him happened as part of a peace treaty.

[18] It is more likely that the marriage helped Chandragupta extend his political power and dominions, enabling him to adopt the title Maharajadhiraja.

[20] Modern historians have attempted to determine the extent of his kingdom based on the information from the Puranas and the Allahabad Pillar inscription issued by his son Samudragupta.

[20] Nevertheless, the information from the inscription can be used to determine the territories that were not a part of Chandragupta's kingdom:[23] A passage in the Vayu Purana states that the Guptas ruled over Saketa (modern Ayodhya), Prayaga, and Magadha.

[26] Scholars critical of this theory argue that the passage describes the territories of either the dynasty's founder Gupta or its 6th century rulers who oversaw the kingdom's decline.

The corresponding passage in the various manuscripts of Bhagavata Purana either does not mention the word "Gupta", or uses it as a common noun meaning "protected" instead of using it as the name of a specific dynasty.

[24] Gold coins bearing portraits of Chandragupta and Kumaradevi have been discovered at Mathura, Ayodhya, Lucknow, Sitapur, Tanda, Ghazipur, and Varanasi in Uttar Pradesh; Bayana in Rajasthan; and Hajipur in Bihar.

[33] It is unlikely that she was a Gupta queen, as the depiction of a female figure seated on a lion is characteristic of a goddess in historical art of India.

[37] The discovery of the coins issued by a Gupta ruler named Kacha have led to some debate about Chandragupta's successor.