Buy the flat, or rent and invest the difference?

How this calculator works

The comparison is only worth anything if both people are treated the same way. Three rules do that work here.

1. Identical money, every single month

Both people start by committing exactly the same cash on day one — the down payment plus stamp duty, registration and everything else the buyer pays to complete the purchase. After that, each month the tool computes what the buyer needs and what the renter needs, takes the larger of the two as a shared budget, and has whoever needs less invest the remainder. Neither person is ever allowed to spend a rupee the other did not. That single rule is what most rent-versus-buy calculators are missing.

2. Somebody always pays for housing

If the buyer lives in the flat, they earn no rent — and the renter has to pay rent for an equivalent home, which is money they cannot invest. If instead the flat is let out, the buyer collects rent but must pay rent on their own home, and so must the renter, so that cost cancels out of the comparison. Pick the mode that matches your actual situation. Giving the buyer rental income while the renter lives free is the most common way these calculators end up flattering property.

3. Both assets compound the same way, and both get taxed on the way out

An annual return means the same thing for both assets: a true compound annual growth rate, converted to a monthly rate the identical way. Quoting property as a CAGR while running equity at a nominal rate divided by twelve silently hands equity an extra 0.7 points a year at 12%, which compounds into a very large number over two decades. Fund fees come off the equity return. At the horizon both positions are liquidated: the flat pays brokerage and capital-gains tax, the fund pays capital-gains tax above the exemption, and any loan still outstanding is settled from the proceeds.

What it counts that simpler tools skip

• Purchase friction — stamp duty, registration, brokerage and legal costs, which are sunk on day one but do lift the capital-gains cost base.
• Home-loan tax relief — interest under Sec 24(b) and principal under Sec 80C, capped, and only under the old regime. The 80C headroom is an input, because most people have already used part of it on EPF and insurance.
• Rental income taxed the Indian way — a 30% standard deduction under Sec 24(a), municipal taxes deducted, loan interest set off, and a cap on how much of a let-out loss can be set against other income, with the excess carried forward. Under the new regime that set-off is not available at all.
• Capital gains on both sides — with a choice between the flat rate and an indexed cost base, and a Sec 54 rollover option.
• Expense ratio — the difference between a direct index fund and a regular plan is roughly 1.5 points a year, which over twenty years is not a rounding error.
• Vacancy, maintenance, municipal tax and periodic repairs — the repairs are capitalised into the cost base, as they should be.
• Prepayment and EMI step-up — because almost nobody actually runs a home loan untouched for twenty years.
• Volatility — a smooth 12% line is a fiction. The risk tab runs the whole comparison across hundreds of simulated return paths and reports how often each answer actually wins.

What it deliberately does not do

It does not price the things that usually decide this question in real life. A home you own cannot be sold in a week, cannot be sold in halves, and is one asset in one city — while a fund can be redeemed on Tuesday. Against that, a house is forced saving, protection from a landlord, and somewhere your family cannot be asked to leave. None of that shows up in a rupee figure, and you should not let a calculator pretend otherwise. Use the number as one input, not as the answer.

It also assumes a fixed loan rate, a fixed marginal tax rate, one lump-sum liquidation at the end rather than a staged one, and that you actually invest the difference every month — which, in practice, is the assumption that fails most often.