The real math, not a guess.
Ask someone what they need to retire comfortably, and you’ll usually get an answer fast. A number, said with real confidence. Two crore. Five crore. Whatever figure feels like “enough.”
Ask them how they arrived at it, and the confidence tends to disappear. Most people built that number by taking what they spend today and rounding up a bit for good measure. It isn’t a calculation. It’s a guess wearing a calculation’s clothes.
There are two specific, very common ways that guess goes wrong, and they both go wrong in the same direction: the real number is almost always bigger than the one people land on.
Here’s the part that’s easy to know intellectually and still get wrong in practice. If you spend ₹1,00,000 a month today, that is not what you’ll spend a month in retirement, 15 or 25 years from now. Prices don’t hold still because you’d prefer them to.
At a fairly typical long-run inflation rate of 6% a year, prices roughly double every 12 years. So the same lifestyle that costs ₹1,00,000 a month today costs somewhere around ₹2,00,000 a month in 12 years, and closer to ₹4,00,000 a month in 24 years, just to buy the same groceries, the same electricity, the same everything.
People who build their retirement number off today’s expense figure aren’t just off by a little. They’re often planning for a lifestyle that will cost roughly double or quadruple what they budgeted for, by the time they actually need the money. This is exactly why a real retirement calculation has to work in real, inflation-adjusted terms, not just take today’s number and multiply it by a round figure of years.
This is the one that catches even people who understand inflation perfectly well. A retirement number built off a monthly budget only captures monthly things: rent or maintenance, groceries, utilities, the recurring bills. It quietly leaves out everything that happens occasionally but still costs real money.
A wedding gift for a close friend’s child. The flight and hotel for that wedding, if it’s not in your city. A car’s tires, which need replacing roughly every four years, not every month, but they still need replacing. A major home repair. An appliance that finally gives out. An unplanned medical expense that insurance doesn’t fully cover. A trip you didn’t budget for but will absolutely want to take.
None of these show up if you only ever ask “what do I spend in a typical month.” They only show up if you deliberately go looking for them, because by definition they don’t happen in a typical month. And because they don’t happen often, it’s easy to convince yourself they don’t count, right up until several of them land in the same year and the budget doesn’t hold.
A genuinely complete expense picture has to include an allowance for exactly this category, not as an afterthought, but as a real, estimated, recurring line item, even though no individual item in it happens every month.
Picture two people who each estimate they need ₹1,00,000 a month to live comfortably in retirement.
The first person takes that number, ignores inflation, ignores the lumpy expenses, and calculates a corpus based on ₹1,00,000 a month, forever, starting now.
The second person adjusts that same starting lifestyle for inflation over their actual retirement horizon, and adds a genuine allowance for the irregular expenses they’ll actually face. Their real required monthly figure, properly projected, ends up meaningfully higher than ₹1,00,000, not because their lifestyle changed, but because the first calculation was never measuring the real thing to begin with.
Same starting lifestyle. Very different corpus. The gap between what these two people think they need and what they actually need can be the difference between a retirement that works and one that runs into trouble in year twelve.
This is exactly why we built two separate calculators rather than one. The Financial Freedom Number Calculator works out the corpus you’d need for your current expenses to be sustained indefinitely, on a real, inflation-adjusted basis. The Retirement Corpus Calculator goes further, factoring in your specific age, life expectancy, and how you want your money invested, to size a corpus that carries you through your actual retirement years.
Both of them do the inflation math correctly by design. Neither of them can fix an incomplete expense number, because that part depends on you actually sitting down and building a real, honest picture of what you spend, including the parts that don’t happen every month.
That’s the step most people skip. Not the calculation. The honest inventory that goes into it.
Before you put a monthly expense figure into either calculator, take twenty minutes and build a genuinely complete list. Start with the obvious monthly items. Then go further: what did you spend on gifts and celebrations last year, spread across twelve months? What large item needed replacing in the last five years, and when’s the next one due? What trip did you take that wasn’t in the original budget? Add a realistic monthly allowance for all of it, not just the bills that arrive on schedule.
Failing to plan is planning to fail. But just as often, the failure isn’t in the planning itself. It’s in planning around a number that was never actually complete.
If you want a second pair of eyes on your own number, especially the parts that are easy to miss on your own, that’s exactly the kind of conversation worth having properly.
Not a rough guess. A real, inflation-adjusted number that accounts for the expenses you haven’t thought of yet.
Book a Discovery CallKaushik Kar, CFP® is an AMFI Registered Mutual Fund Distributor (ARN: 270609). Mutual fund investments are subject to market risks; read all scheme-related documents carefully. This website is for informational purposes only and does not constitute investment advice or a solicitation to buy or sell any security.