FIRE Number Calculator

A worked example: Divya, 34, in Pune

Divya works in a product company in Kharadi and spends about ₹65,000 a month, all-in. Rent on a 2BHK, groceries from the BigBasket cart, the odd Swiggy order, a Bajaj Chetak EMI, a ClearTax subscription she forgets to cancel. She doesn't track every rupee but she knows the number from her bank statement, roughly, and that's enough to start.

Annual expenses: ₹65,000 × 12 = ₹7,80,000. Divide by 3.3% and you get ₹2,36,36,364, call it ₹2.36 crore. That's her FIRE number in today's rupees. Not the number she'll actually need on the day she retires, which will be higher because of inflation between now and then, but the number the calculator uses as the target she has to reach.

She has ₹28 lakh already invested, split across two Nifty index funds and an EPF balance she mostly ignores. She puts in ₹45,000 a month. Punch that into the calculator above with a 12% return assumption and it'll tell you roughly when ₹28 lakh growing at 12% a year, topped up by ₹45,000 monthly, crosses ₹2.36 crore. For Divya that comes out to her late forties. She was hoping for early forties. The gap between those two numbers is the whole point of running this calculator more than once, with different SIP amounts, before deciding anything.

What the number means, and what it doesn't

The FIRE number is a target corpus, in today's purchasing power, at which a 3.3% withdrawal covers your current lifestyle. It is not a guarantee. It is not the amount that will make you happy or the amount your parents think you need before you stop working. It is arithmetic applied to the expenses you typed in, nothing more.

It also doesn't know about the year you'll actually hit it. If Divya reaches ₹2.36 crore in 2038, that ₹2.36 crore buys 2026-level goods and services only if her expenses have been re-run for inflation along the way, which the growth projection above does account for on the target side but you still have to keep re-checking your actual monthly spend as years pass. A FIRE number calculated once at age 30 and never revisited is a number about a life that no longer exists by 40.

Mistakes people make with this calculator

The most common one: entering take-home salary where expenses should go. The calculator asks what you spend, not what you earn, and the two numbers can be very different for someone with a high savings rate.

Second, people forget one-off categories that recur every few years, not every month, and so never make it into a monthly average. Foreign travel every second year. A new laptop. Replacing the car in year eight. None of these show up in a casual mental tally of "monthly expenses" but they show up on the bank statement eventually.

Third, people set the return assumption to something like 15% because that's what their portfolio did over the last three years, and three years is not a long-term CAGR, it's a bull run. The default of 12% is already the generous end of Nifty 50's long-run history.

Where this breaks down

This calculator assumes constant returns, compounding smoothly, year after year. Real markets don't do that. A 2020-style crash in year three of your accumulation phase changes your actual trajectory in ways a single CAGR number can't show you. This tool doesn't model sequence risk at all during accumulation, only the SWP calculator touches that, on the withdrawal side.

It also assumes your expenses stay roughly the same shape after retirement as before, which is often false. Commuting costs usually fall. Healthcare costs usually rise, sometimes sharply, and this calculator doesn't separate the two. If a large share of your projected retirement spend is medical, a flat inflation-adjusted number understates the risk, because medical inflation in India has historically run well above general CPI. Treat the output as a first estimate you refine, not a figure to bank a resignation letter on.