PPF calculator

The Public Provident Fund is a 15-year government-backed savings scheme run by the Department of Economic Affairs and operated through India Post and authorised banks. Deposits earn a quarterly-revised rate (currently 7.1%), are EEE-tax-treated (Exempt at contribution, Exempt on interest, Exempt at maturity), and have a hard ₹500–₹1,50,000 annual deposit window per account.

Interest is computed monthly on the eligible balance, but credited only at the end of each financial year (end of March). A generic compound-interest calculator that compounds monthly will overshoot the real maturity, and a calculator that compounds annually on an end-of-year balance will undershoot it. The faithful answer requires a month-by-month simulation — which is exactly what this engine does.

A deposit made on or before the 5th of any month counts toward that month's eligible balance; a deposit made after the 5th doesn't earn interest until the next month. On a 150,000/year contribution over 15 years, the after-5th path loses about a month's worth of interest on every installment — the timing-comparison table shows the gap directly. This is the single most underappreciated PPF lever; most casual investors don't know it exists.

The April lump sum wins — by a non-trivial margin. The full annual cap deposited in April earns 12 months of monthly interest in the first FY; a monthly drip only gets the full year on the April installment and progressively less on each later one. Over 15 years, the lump-sum path beats the drip by roughly 1.2 lakh of the chosen currency on the same 150,000/year outlay. The frequency-comparison table makes this explicit so users stop assuming monthly SIPs into PPF are equivalent to a yearly lump sum.

Base lock-in is 15 years. After maturity you can extend in 5-year blocks indefinitely; extensions can be with or without further contributions. The engine accepts tenure = 15, 20, 25, 30, … years (15 + n × 5); non-block lengths are rejected at validation. v1 always simulates extensions WITH further contributions at the chosen frequency.

PPF is in the EEE bracket: contributions up to 150,000/year are eligible under Section 80C, interest accrues tax-free, and the maturity amount is tax-free. The catch: Section 80C is a shared 150,000 ceiling across PPF, ELSS, ULIPs, life-insurance premiums, EPF, NSC, principal repayment on home loans, etc. — not per instrument. This calculator labels the eligible amount; it does not give personalized tax advice.

Only PPF. The contract is fundamentally different from each: an FD is a bank deposit with a fixed contractual rate over a chosen tenure; a SIP is a market-linked equity-fund investment with no guaranteed rate; PPF is a sovereign-backed scheme with a quarterly-revised rate, a 15-year lock-in, a ₹1.5 L annual cap, and EEE tax treatment. Conflating them on one page tends to mislead — there are dedicated pages for FD, SIP, and FD-vs-stock comparison.

A generic compound-interest calculator gives you FV = P × (1 + r/n)^(n × t) and stops. This engine encodes PPF scheme rules: the 500–150,000 window is enforced as validation; the deposit frequency drives a real installment schedule (yearly = April lump sum, monthly = 12 installments, etc.); the 5th-day rule is implemented as a per-deposit eligibility test; interest accrues monthly and credits annually in March; tenure is restricted to 15 + n × 5. The transparency layer matches the rest of the suite — every output traced, every input audited.