Retirement planning is usually presented as product shopping; it is actually three numbers and a decision. The three: what you will spend in your first retired year, the corpus that number implies, and the withdrawal rate you can safely run. The decision is what to do about the gap between the third number and your current plan. Ten minutes of arithmetic — with stated assumptions — beats an hour of fund comparisons, so here is the whole calculation.
Number one: what will you spend?
Take today's retirement expenses — say ₹1 lakh a month — and inflate them to your retirement date. India's CPI print ran at 5.54% in September 2026 (Ministry of Statistics' provisional estimate) against the RBI's 4% target band, and planning analyses (freefincal's, among others) argue for 6–7% pre-retirement inflation because lifestyle inflation runs hotter than the index. At 6% for 25 years, ₹12 lakh a year becomes about ₹51.5 lakh in the first retired year. If that seems brutal, the honest answer is that it is — the alternative is assuming away the problem. Our real-returns page shows why this step dominates everything that follows.
Number two: what corpus does that imply?
Divide the first-year expense by your withdrawal rate. At 4% — the rule William Bengen derived from US data in his 1994 Journal of Financial Planning study — ₹51.5 lakh implies about ₹12.9 crore. At 3%, which Indian analyses argue is the safer end given higher and more volatile inflation than the US, it implies ₹17.2 crore. The withdrawal rate is the assumption that moves this number more than anything except the horizon, which is why the ₹10-crore question is really a withdrawal-rate argument in disguise.
Number three: can you get there?
The accumulation arithmetic is unforgiving and worth seeing once: ₹25,000 a month for 25 years at an assumed 12% builds roughly ₹4.7 crore — not even half the ₹12.9 crore target. The gap closes with the levers in order of reliability: start earlier (time beats rate), step up the SIP with income (a 10% annual step-up changes the destination more than a return chase), and count the wrappers you already own — EPF, PPF, NPS — rather than asking one SIP to do everything. The retirement calculator and the FIRE planner run your own numbers; the formulas are theirs, not this page's job.
The three numbers, worked
The full chain from today's expenses to the implied corpus and the monthly amount that closes the gap. Assumptions are stated; the calculators run your own.
View the numbers as a table
| Step | Assumption | Result |
|---|---|---|
| Today's retirement expense | ₹1 lakh/month | ₹12L/yr |
| First retired year | 6% inflation × 25 years | ≈ ₹51.5L/yr |
| Corpus at 4% withdrawal | Bengen 1994 origin; Indian analyses argue 3-5% | ≈ ₹12.9 Cr (3% → ₹17.2 Cr) |
| What ₹25K/mo for 25y builds | Assumed 12% p.a. | ≈ ₹4.7 Cr — the gap is the plan |
| Gap-closers | Earlier start, step-up SIP, count EPF/PPF/NPS | Each lever beats a return chase |
Inflation inputs: MoSPI CPI (Sept 2026: 5.54%) and the RBI 4% target; planning guidance for 6-7% pre-retirement inflation is third-party analysis (freefincal). Withdrawal-rate history: Bengen (JFP, Oct 1994); Indian 3-5% ranges are third-party analyses. Illustrations, not forecasts.
Then what? Drawing it down
Accumulation and decumulation are different problems with opposite instincts, and the corpus must survive both inflation and the order of returns. The short version: a systematic withdrawal plan from funds taxes only the gain component of each redemption — a structural advantage over FD interest, which is taxed in full at slab — and the sequencing risk (a crash in the first retired years) is managed with cash buckets, not with hope. The full drawdown comparison — SWP versus annuity versus FD ladders — is its own page: which products to draw from.
Where the plan actually breaks
- Inflation assumption too polite. Planning at 4% when your lifestyle inflates at 7% is a 25-year walk off a cliff that only appears at the edge.
- Horizon too short. Life expectancy at 60 runs about 17.5 years for men and 19 for women (LASI+SRS-based analysis) — and averages mean half the population outlives them. Planning to 85–90 is not pessimism; it is the median case for a couple, since one spouse usually outlives the other.
- The corpus that exists only in Excel. EPF balances never transferred, old folios unlinked, insurance "savings" counted at face value — the plan runs on audited numbers, not remembered ones. The portfolio X-Ray exists for exactly this audit.
- Withdrawals that ignore sequence. The first three retired years matter more than the next thirty — a fixed withdrawal through a crash locks losses in. Guardrails and cash buffers are the defence.
The ten-minute version ends where the calculators begin: your expenses, your horizon, your corpus — three numbers, one gap, and a monthly amount that closes it. Everything else is product selection, and product selection is the easy part.
Educational content, not financial advice. Inflation figures from MoSPI's September 2026 CPI release; the RBI's 4%±2% target per the MPC framework; life-expectancy figures from the LASI+SRS-based study as reported by Down To Earth (third-party); withdrawal-rate history from Bengen's October 1994 Journal of Financial Planning study with Indian 3–5% ranges from freefincal's published analyses (third-party, labelled). The worked example is this page's arithmetic on stated assumptions. All figures checked 29 October 2026.