What is a retirement corpus?
A retirement corpus is the total amount you need to have saved by the time you retire to sustain your lifestyle for the rest of your life. It must be large enough to cover escalating expenses — because inflation does not stop when you stop working — while your remaining corpus continues to earn returns.
The corpus requirement depends on five variables: your current age, your planned retirement age, your life expectancy, your current monthly expenses, and the assumed rates of inflation and post-retirement returns. Small changes in any of these inputs produce significantly different results, which is why personalised calculation matters.
How the corpus is calculated
This calculator uses the growing annuity formula, which accounts for the fact that your annual expenses will rise with each year of retirement due to inflation. Key steps:
First, your current monthly expense is projected forward to retirement age using the assumed inflation rate. This becomes the annual expense at retirement. Then, the growing annuity formula calculates the corpus required today such that, earning the post-retirement return rate, it can fund a stream of annually increasing withdrawals for the expected duration of retirement.
The expense multiplier (e.g., “30x”) is a quick-reference metric — it shows how many times your first-year retirement expense the total corpus represents. A 30x corpus at a 7% post-retirement return with 6% inflation typically sustains about 25–30 years of retirement.