What Is PPF and How Its Interest Is Calculated
The Public Provident Fund (PPF) is one of India's most popular long-term savings schemes, and for good reason: it offers steady, government-backed returns, generous tax benefits, and the quiet power of compounding over 15 years. But many people deposit into it without understanding how the interest is actually worked out — and that single detail can change how much you earn.
What PPF is
PPF is a government savings scheme open to any resident individual. You can open one account at a bank or post office, deposit between ₹500 and ₹1,50,000 per financial year, and the balance earns a fixed rate of interest set by the government each quarter. The account runs for 15 years, after which you can withdraw the full amount or extend in blocks of five years. Both the interest earned and the maturity amount are tax-free, which makes the effective return higher than the headline rate suggests.
How PPF interest is actually calculated
Here is the crucial part most people miss. PPF interest is calculated every month on the LOWEST balance in your account between the 5th and the last day of that month. The interest is computed monthly but credited only once, at the end of the financial year. Because the calculation looks at the lowest balance after the 5th, the date you deposit matters a great deal.
Why deposit timing changes your returns
Suppose you deposit ₹1,50,000 as a lump sum. If you put it in on or before the 5th of the month, that full amount counts towards the lowest balance and earns interest for that whole month. Deposit it on the 6th or later, and the deposit earns no interest for that month at all — the lowest balance between the 5th and month-end ignores money added after the 5th. Over many years this small habit adds up to a meaningful difference. The simple rule: always deposit before the 5th of the month, and ideally before the 5th of April to capture interest for the entire financial year.
How the compounding builds up
PPF compounds annually, so each year's interest is added to your balance and then itself earns interest the following year. Deposit ₹1,50,000 every year at an assumed 7.1% rate and over 15 years you contribute ₹22,50,000 of your own money — but the maturity value works out to roughly ₹40,68,000. The extra ₹18,00,000 or so is pure compounding, earned tax-free.
Smart ways to use a PPF account
- Deposit early — before the 5th of the month, and before 5 April for the year's first deposit, to maximise interest.
- Contribute the full ₹1,50,000 limit if you can; it is also the cap for tax deduction under the scheme.
- Treat it as a long-term, leave-it-alone investment — the 15-year lock-in is a feature, not a flaw.
- Use the extension option at maturity to keep the tax-free compounding running if you do not need the money.
The bottom line
PPF rewards patience and good timing. Because interest is calculated on the lowest balance after the 5th, depositing early in the month — and early in the year — quietly boosts your returns, while 15 years of tax-free compounding does the heavy lifting. Model your own contributions with our PPF calculator to see exactly what your discipline will be worth at maturity.