What is the Retirement Income Calculator?
A retirement income calculator answers the opposite question to a retirement planning calculator: instead of asking how much you need to save, it takes the corpus you already have and works out how much income it can pay you, how long it will last, and the age at which it might run out. It is a drawdown (decumulation) tool that helps you turn a lump sum into a sustainable, inflation-aware monthly income.
How does it work?
You enter your corpus, your age, life expectancy, the monthly expense you want to cover (in today’s money), how fast that expense should rise each year, your risk profile and any income such as a pension. Month by month, the calculator grows your corpus by its expected return and subtracts your withdrawal (net of your income), increasing the withdrawal once a year. It tracks the balance until your life expectancy — or until the money runs out — and also solves for the maximum spending level your corpus could sustain for the full plan.
Formula
Balanceₘ = Balanceₘ₋₁ × (1 + r/12) − (Wₘ − I)
- Balanceₘ = corpus balance at the end of month m
- r = post-retirement annual return (from risk profile)
- Wₘ = monthly withdrawal, stepped up each year
- I = monthly income (pension/annuity/rent)
Example calculation
A 60-year-old with a ₹1 crore corpus who wants ₹60,000 a month rising 6% a year, invested at a balanced 7.5%, would see the corpus run out at about age 76 — nine years short of an age-85 plan. The calculator shows that a sustainable spend would be closer to ₹42,000 a month, or that adding a ₹20,000 pension stretches the corpus to around age 81.
Benefits
- Tells you immediately whether your corpus can sustain your lifestyle, and for how long.
- Solves for a safe spending level instead of making you guess and re-check.
- Shows the run-out age visually and compares conservative, balanced and aggressive profiles.
Limitations
- Assumes a steady return; a market fall early in retirement can shorten longevity (sequence-of-returns risk).
- Ignores taxes and treats your income as fixed for life.
- Does not model irregular or one-off expenses such as medical events.
Conclusion
Knowing your corpus is only half the picture — what matters in retirement is the income it can safely deliver without running dry. Use this calculator to pressure-test your spending, find a sustainable withdrawal and see how risk and extra income change the outcome. If the projection falls short of your life expectancy, the Retirement Planning Calculator can help you work out how much more corpus to build.