The formula, and the two numbers that actually decide it

Take a household spending ₹80,000 a month. That’s ₹9.6 lakh a year, and the corpus target depends entirely on the withdrawal rate:

Same household, same spending, and the target moves by ₹80 lakh — a third of the whole number — purely on an assumption. It is one of the two inputs that move the answer most, and most tools set it silently to 4%.

Then inflation moves it again

The figures above are in today’s rupees. If you plan to stop working in 20 years, you won’t be spending ₹9.6 lakh a year by then — you’ll be spending whatever ₹9.6 lakh becomes after two decades of inflation.

Two percentage points of inflation — the width of the upper half of RBI’s own tolerance band — adds about 46% to the corpus you need. Over 30 years, moving a single point from 4% to 5% adds roughly 33%. Only the withdrawal rate moves the answer as much, which is why a plan is only as good as the assumptions it states out loud.

Why the 4% rule doesn’t answer an Indian question

The 4% figure isn’t a law of finance. It comes from research into historical US market returns, testing how often a portfolio survived a 30-year retirement while the retiree withdrew an inflation-adjusted 4% a year. Within that frame it held up well, and it became shorthand everywhere.

Three things change when you move the question to India.

The horizon is longer

The whole point of FIRE is retiring early. Someone stopping work at 35 is not funding 30 years — they may be funding 50. A longer horizon means more sequences of bad returns to survive, and mathematically it supports a lower withdrawal rate, not the same one. Using a 30-year answer for a 50-year problem is a structural error in FIRE planning, whichever country you plan in.

The safety net is different

The original work sat inside an economy with state-backed retirement income and, for retirees, public health cover. India has no comparable universal backstop, so a medical event in year 18 is a corpus event rather than an insurance event. That argues for a larger buffer, held deliberately, rather than a tighter number.

The return and inflation history is different

A rule derived from one country’s equity, bond and inflation history is a statement about that history. Indian equity returns and Indian inflation have their own distributions, and there is no reason a constant fitted to one should be a constant in the other. That’s not an argument that Indian outcomes are worse — it’s an argument that borrowing the number without re-deriving it is unjustified.

Put together: 4% is a reasonable ceiling to test against, not a floor to plan on. Many Indian FIRE plans that look tight at 4% look sane at 3.5% and comfortable at 3% — and the difference between those three is entirely a judgement about how much certainty you want to buy.

Lean, Coast and Fat FIRE

These aren’t different formulas. Two of them are the same formula with a different expense base; the third is a genuinely different idea.

Coast FIRE comes before full independence, often by years, and it is easy to pass without noticing. It isn’t retirement — you keep working — but you stop having to save. You reach it when your current corpus, compounded at your assumed return for the years remaining, arrives at your FIRE number on its own. It reframes the goal from a distant date into something you can cross in your thirties, and it’s the reason the projection is worth running even when full independence looks far off.

How to actually run it

1. Find your real annual expenses. Three months of actual spending, not a budget you intend to follow. Guessing this is the most common reason a FIRE plan is wrong — and it’s why automatic expense tracking comes first.
2. Choose a withdrawal rate, deliberately. 25× at 4%, 28.6× at 3.5%, 33.3× at 3%. Write down which you chose and why.
3. Inflate the target to your retirement year. Grow the annual figure at your assumed inflation for the years remaining, then apply the multiple to that.
4. Compare against what you already have. Your existing corpus compounds by itself; your monthly contribution compounds on top. That gap gives you the date — which needs an honest net worth figure to start from.

What most FIRE calculators get wrong

• Hiding the withdrawal rate. If a tool doesn’t let you change it, it has made the most important decision on your behalf.
• Using a budget instead of actual spending. The input is what you spend, not what you meant to spend.
• Ignoring inflation, or hard-coding it. A calculator that can’t show you the 4% and 6% cases isn’t modelling the risk that matters most.
• Counting the family home in the corpus. Real net worth, but it can’t fund a withdrawal. Most tools invite this: with no field for the house, people type it into “other assets”. Our retirement planner gives the residence its own field and then excludes it from every projection.
• Counting the emergency fund twice. Money you would have to spend in a bad month is not retirement corpus, and a target that includes it assumes a cushion you no longer have. The planner carves it out first, sized by whether your income is government, salaried or self-employed.
• Treating an average return as an experienced return. A long-run average is not what any individual investor lives through; the order in which returns arrive matters, especially in the first years of drawdown. The SIP-versus-EMI arithmetic makes the same point about averages from the other direction.
• Holding one rate of return flat for thirty years. This calculator does it too. A fund built to de-risk on a schedule does the opposite deliberately — SEBI’s new life cycle funds publish the exact bands their equity has to fall through as the target year nears, which is a useful check on any projection that assumes 11% all the way to 60.

The calculator above is deliberately the short version: a few inputs and one number. If you want the long one — the emergency fund carved out before anything is projected, your home loan amortised to the month it closes, NPS locked until 60, capital gains tax on withdrawals, and a probability rather than a single figure — that lives on the retirement planner. It is the same arithmetic, taken as far as it goes.

How TLDR Money does it

TLDR Money will show your FI number, how far along you are, and a projected retirement date — modelled for Lean, Coast and Fat FIRE.

The reason it sits in the same product as spending and net worth is that a FIRE projection is only as good as its two inputs. It needs your real annual expenses, which comes from automatically tracked spending rather than a guess, and your real current corpus, which comes from a net worth figure that includes everything. Kept in separate apps, those two numbers are estimates, and a projection built on two estimates inherits both errors. That’s the argument for one product doing all three: the platforms with the best tracking mostly don’t model spending, and the spending apps mostly don’t model independence.

TLDR Money will earn from the subscription alone — no ads, no referrals, no fund commissions, no lending arm. See how we make money.

Everything in this cluster

Questions worth asking

How do I calculate my FIRE number in India?

Take your real annual expenses and divide by the withdrawal rate you are willing to rely on. At 4% that is 25 times annual expenses; at 3.5% it is roughly 28.6 times; at 3% it is about 33.3 times. Then inflate that figure to the year you actually plan to stop working, because your expenses then will not be your expenses now. The arithmetic is simple — the difficulty is that the answer is extremely sensitive to two assumptions most calculators bury.

Does the 4% rule work in India?

It was not built for the question most Indian savers are asking. The 4% figure comes from studies of historical US market returns over rolling 30-year retirements. Someone retiring at 35 in India is planning for perhaps 50 years, not 30, and a longer horizon mathematically supports a lower withdrawal rate. There is also no state healthcare backstop of the kind the original work implicitly assumed. None of that makes 4% impossible — it means it is a US answer to a US question, and treating it as a universal constant is the actual error.

What inflation rate should I assume for a FIRE plan in India?

Plan against the policy framework rather than this month’s print. RBI’s mandate is 4% CPI inflation with a tolerance band of 2% to 6%, retained for the period from April 2026 to March 2031. Actual inflation moves around inside that band — it was 3.48% in April 2026 — but a retirement plan spanning decades should not assume the low end of a band persists for decades. Assuming the 4% target, and testing what happens at the 6% ceiling, is more useful than picking a single optimistic figure.

How much does the inflation assumption change my FIRE number?

Far more than people expect, because it compounds. Over 20 years, assuming 6% inflation instead of 4% raises the expenses you need to fund by about 46%, and therefore raises your corpus target by about the same proportion. Over 30 years, moving just one percentage point from 4% to 5% raises it by roughly 33%. This is why an assumption buried in a calculator’s defaults matters more than the precision of any other input.

What is the difference between Lean, Coast and Fat FIRE?

They are the same arithmetic with different inputs. Lean FIRE targets a deliberately low expense base, so the corpus is smaller and reachable sooner, with less margin for error. Fat FIRE targets a comfortable expense base and therefore a much larger corpus. Coast FIRE is different in kind: it is the point where what you have already invested will compound to your full number by your target age without you adding another rupee — so you still work, but you no longer have to save.

Can I include my house in my FIRE corpus?

Not the one you live in. A home you occupy is genuine net worth but it cannot produce the income you plan to withdraw, and you cannot sell it without needing somewhere else to live. Counting it toward a FIRE corpus is a common way people conclude they are far closer to financial independence than they are. Property you rent out is different, because it produces income — value the equity, and count the rent, not the notional sale price.

Sources

• Reserve Bank of India monetary policy framework — flexible inflation targeting, 4% CPI target within a 2–6% tolerance band, introduced via the 2016 amendment to Section 45ZA of the RBI Act, 1934 — rbi.org.in
• PRS India, “Review of Monetary Policy Framework by RBI” — prsindia.org
• India retains the 4% inflation target with a 2–6% band for April 2026 to March 2031 — drishtiias.com
• India CPI inflation, 3.48% in April 2026 — tradingeconomics.com

Every figure above is arithmetic on stated assumptions, and the assumptions are the point — change them and the answer changes materially. Returns are not guaranteed, projections are illustrations rather than forecasts, and this is an explanation of how the calculation works, not advice about your own money. TLDR Money is not a registered investment adviser.