Yes, this is authentically established. The Prophet ﷺ said to a woman of the Anṣār who was unable to perform Hajj with him: "Perform Umrah when Ramadan comes, for Umrah in Ramadan is equal to a Hajj" (Sahih al-Bukhari 1782), and in the narration about Umm Sinān al-Anṣāriyyah the wording is "an Umrah in Ramadan is equal to a Hajj with me" (Sahih al-Bukhari 1863). The scholars are agreed, however, that this refers to equality in reward, not that it removes the obligation of Hajj from the one who is able: whoever performs Umrah in Ramadan still owes the Hajj of Islam, for Allah says: "And due to Allah from the people is Hajj of the House — for whoever is able to find a way to it" (Quran 3:97). So it is a tremendous virtue and an encouragement, not a substitute.
Q&A · Hajj
Is it true that Umrah in Ramadan equals a Hajj in reward?
Evidence — the daleel
On deen2u
Informational, not a personal fatwa. Consult a qualified scholar for rulings on your situation.