Worked example
Example with the default numbers — change them above.
Your age today: 30 · Age you want to retire: 42 · Monthly spending today: ₹60,000 · Lean FIRE monthly budget (today's money): ₹42,000 · Investments today: ₹15,00,000 · Monthly saving and investing: ₹50,000 · Assumed return per year: 11% · Inflation per year: 6% · Withdrawal rate in retirement: 3.5%
On a Lean FIRE budget of ₹42,000 a month, your Lean FIRE number is ₹1.44 Cr in today's money (₹2.9 Cr by age 42). Investing ₹50,000 a month, you reach it in 13 yrs 7 mo (age 43), 1 yr 7 mo after your target age of 42.
| You reach Lean FIRE | Age 43 · In 13 yrs 7 mo |
|---|---|
| Lean FIRE number at 42 | ₹2.9 Cr · ₹1.44 Cr in today's money, 28.6× yearly spending |
| Gap at age 42 | ₹39.38 L · Projected investments ₹2.5 Cr |
| Monthly saving to retire at 42 | ₹59,949 · First year, rising 7% a year |
| Monthly spending at 42 | ₹84,512 · Today's ₹42,000 after 6% inflation |
| Compared with regular FIRE | 4 yrs 2 mo sooner · Regular FIRE number ₹2.06 Cr in today's money |
How the Lean FIRE Calculator works
- Your lean monthly budget, in today's rupees, is inflated to each future year at your inflation rate.
- The Lean FIRE number is that yearly budget divided by your withdrawal rate.
- Your investments grow monthly with your saving, raised once a year, at your expected return.
- The age you reach Lean FIRE is the first month your investments meet the rising target.
- The same steps run for your current spending, so you can see the years a lean budget saves and what it costs in cushion.
Lean FIRE number
Lean FIRE number at age A = 12 × B × (1 + i)^(A − current age) ÷ w
B = lean monthly budget in today's money
i = inflation; w = withdrawal rate
Regular FIRE uses today's spending S in place of BAssumptions and limits
- You can actually live on the lean budget for decades, including as your needs change with age.
- Returns are the same every year; real markets rise and fall.
- Spending rises with the inflation you enter; healthcare often rises faster.
- The 70% default for the lean budget is a site convention for illustration, not a standard definition of Lean FIRE.
- Tax is not modelled; enter returns after costs.
Frequently asked questions
What is Lean FIRE and how much do I need in India?
Lean FIRE is early retirement on a frugal budget, usually close to essential costs. The corpus needed is your yearly lean budget divided by your withdrawal rate. A household living on ₹35,000 a month would need about ₹1.2 crore in today's money at a 3.5% withdrawal rate. City, family size and whether you own your home change the right budget a lot.
How much lower should a Lean FIRE budget be?
There is no fixed rule. This calculator starts the lean budget at 70% of what you spend today, purely as an illustration. A better method is to list your essentials, such as housing costs, food, utilities, transport, insurance and modest leisure, and add a margin. If the lean budget only works by cutting things you value, the extra years of work may be worth it.
Is Lean FIRE realistic in an Indian metro?
It can be, mainly for people who own their home and have few dependants. Rent alone can make a lean budget hard in Mumbai, Delhi or Bengaluru, which is why some Lean FIRE planners move to a smaller city after retiring. Price your actual lean life in the city you will live in, and include health insurance premiums.
Should I use a lower withdrawal rate for Lean FIRE?
Many planners do. With a lean budget there is little discretionary spending to cut when markets fall, so you cannot easily spend less in bad years. A lower withdrawal rate, such as 3% instead of 3.5%, builds in more cushion at the cost of a bigger corpus. Try both here and check the result in the FIRE Monte Carlo simulator.
What are the biggest risks of Lean FIRE?
Three stand out. First, little room to cut spending in a bad market. Second, healthcare: one hospital stay that insurance does not fully cover can be a large share of a small corpus. Third, lifestyle drift: frugal at 35 may feel different at 55 with ageing parents or children's education. Health cover, a separate buffer and willingness to earn some income reduce these risks.
Can I move from Lean FIRE to regular FIRE later?
Yes. Some people stop full-time work at Lean FIRE and keep earning a little, letting the corpus grow towards a regular FIRE number. Others work a few more years first. The comparison on this page shows how many extra years regular FIRE takes on your current saving, which helps you judge whether the earlier exit is worth the thinner margin.
Sources
- Ministry of Statistics and Programme Implementation: consumer price index (inflation) data
- Reserve Bank of India: inflation, interest-rate and household-finance statistics
- AMFI: mutual fund data and investor education (SIP and SWP basics)
- SEBI: investor education on market risk
Logic and rates last verified on .
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Guides that go deeper
See worked examples
The corpus and monthly SIP to retire at 40, 45, 50 or 55 on ₹20,000 to ₹2 lakh a month.
- How much corpus do I need to retire at 40 with ₹20,000 monthly expenses? — Corpus ₹1.23 Cr, SIP ₹44,500 a month
- How much corpus do I need to retire at 40 with ₹30,000 monthly expenses? — Corpus ₹1.84 Cr, SIP ₹66,500 a month
- How much corpus do I need to retire at 40 with ₹50,000 monthly expenses? — Corpus ₹3.07 Cr, SIP ₹1,11,000 a month