How the PPF Calculator works
The Public Provident Fund (PPF) is a long-term, government-backed savings scheme available to Indian residents. You deposit a fixed amount each financial year, the government declares an interest rate every quarter, and interest compounds annually on the balance. This calculator projects the maturity corpus from a level yearly deposit, a chosen interest rate, and the number of years invested.
The formula
PPF interest is credited on the lowest balance between the 5th and last day of each month, but for a level annual deposit made at the same point each year, the standard simplification is the future value of an annuity due:
M = P × (((1 + i)n − 1) / i) × (1 + i)
where P is the fixed amount deposited every year, i is the annual interest rate expressed as a decimal (for example 0.071 for 7.1%), and n is the number of years the deposits continue. The trailing (1 + i) factor applies when each deposit is made early in the PPF year (on or before the 5th of April), so it earns interest for the full year; if you deposit at the end of the year instead, the calculator drops that factor and uses the plain ordinary-annuity formula M = P × (((1 + i)n − 1) / i).
Worked example
Depositing Rs 1,50,000 every year for 15 years at 7.1% annual interest, with deposits made at the start of each PPF year, gives i = 0.071 and n = 15. The formula produces a maturity value of roughly Rs 40.7 lakh. Total contributions over 15 years are Rs 22.5 lakh, so the account earns about Rs 18.2 lakh in interest — a wealth-gain multiple of roughly 1.8 times the amount deposited.
PPF rules this calculator assumes
- Deposit limits: the Indian government caps PPF deposits between Rs 500 and Rs 1,50,000 per financial year; amounts above the cap do not earn interest.
- Lock-in period: a PPF account matures after 15 financial years from opening, and can then be extended in blocks of 5 years, with or without further deposits.
- Interest rate: set quarterly by the government; it has held at 7.1% per annum since April 2020, but this calculator lets you test any rate to model past or future scenarios.
- Compounding: interest compounds annually and is credited to the account at the end of each financial year.
What moves the maturity value most
Tenure has an outsized effect because compounding needs time to work: extending the same deposit from 15 to 25 years roughly doubles the maturity value, not just adds ten more years of deposits. The interest rate matters too — since the rate is set quarterly by the government and has ranged from below 7% to above 8% historically, running the calculator at both a lower and a higher rate gives a realistic band for long-range planning. This tool performs pure compound-interest arithmetic only; it does not model taxes, partial withdrawals, loans against the balance, or discretionary top-ups in a single deposit year, all of which a real PPF account may involve.