Question: I'm retiring with a corpus of ₹1,00,00,000. I plan to withdraw a fixed ₹80,000 every month, and the remaining corpus is expected to earn 7% per annum. Roughly how many years will this corpus last before it runs out, assuming I don't adjust withdrawals for inflation?
Answer: Approximately 18.7 years (about 224–225 months).

Supporting evidence:
title: Inline formula / method note
quote: Standard annuity (present value, solved for number of periods) formula — retirement corpus depletion mathematics
context: Standard annuity (present value, solved for number of periods) formula — retirement corpus depletion mathematics.