Overview
The Public Provident Fund (PPF) is India's most trusted long-term savings instrument — government-backed, completely tax-free, and available to every resident Indian. Over a 15-year term, the power of compound interest on a PPF account is dramatic: annual contributions of ₹1.5 lakh (the maximum) at 7.1% produce a maturity corpus of approximately ₹40.7 lakh, entirely tax-free.
Yet most account holders have only a vague sense of what their PPF will be worth at maturity. This article walks through the exact calculation mechanics, the critical rule about the 5th of each month, and how to use the PPF Calculator to project your specific scenario including extensions.
What You Need
- Current PPF account balance — from your passbook, net banking, or the India Post/bank app
- Annual contribution amount — up to ₹1.5 lakh per financial year (can be deposited in up to 12 instalments)
- Current PPF interest rate — 7.1% for FY 2026-27 Q1 (April–June 2026); subject to quarterly revision
- Years remaining to maturity — PPF has a 15-year lock-in from the date of account opening; partial withdrawals allowed from year 7
Steps
Step 1: Understand the PPF interest calculation rule
PPF interest is calculated monthly but credited annually (on 31 March each year). The government calculates interest on the minimum balance between the 5th and last day of each month. This creates a critical rule:
- Deposit before the 5th of any month to earn interest on that contribution for that month
- Deposits on the 6th or later earn no interest for that month — they count from the next month
This single rule has a compounding impact over 15 years. Depositing ₹1.5 lakh on 1 April vs 6 April makes a difference of one full year's interest on that instalment. Over 15 years, consistently depositing on 1 April rather than 30 March results in a meaningfully higher maturity amount.
Step 2: Apply the PPF maturity formula
For fixed annual contributions, the PPF maturity value uses the future value of an annuity formula:
Maturity Value = P × [((1 + r)^n - 1) / r] × (1 + r)
Where:
- P = annual contribution (e.g., ₹1,50,000)
- r = annual interest rate (7.1% = 0.071)
- n = number of years (15)
For ₹1.5 lakh/year at 7.1% for 15 years:
Maturity Value = 1,50,000 × [((1.071)^15 - 1) / 0.071] × 1.071
= 1,50,000 × [(2.799 - 1) / 0.071] × 1.071
= 1,50,000 × 25.34 × 1.071
≈ ₹40.7 lakh
Total amount invested over 15 years: ₹22.5 lakh
Interest earned: ₹18.2 lakh
Tax on the entire ₹40.7 lakh: zero
Step 3: Add your existing balance
If your PPF account already has a balance from prior years, calculate it separately as a lump sum growing for the remaining years:
Future Value of Existing Balance = Current Balance × (1 + r)^n
For example, if you have ₹8 lakh already and 10 years remaining at 7.1%:
₹8,00,000 × (1.071)^10 = ₹8,00,000 × 1.989 = ₹15.9 lakh
Add this to the future value of your ongoing annual contributions for the same 10 years to get the total projected maturity amount. The PPF Calculator handles this combined calculation automatically.
Step 4: Model the extension scenarios
At the end of 15 years, many investors choose to extend their PPF rather than withdraw. Extensions run in 5-year blocks and can be repeated indefinitely. There are two extension types:
Extension with contributions (continuing to deposit up to ₹1.5 lakh/year with 80C benefit):
For our ₹40.7 lakh corpus extended for 5 more years at 7.1% with ₹1.5 lakh/year:
- Corpus growth: ₹40.7 lakh → approximately ₹57.1 lakh
- Plus 5 new contributions of ₹1.5 lakh = ₹7.5 lakh
- Total at 20 years: ≈ ₹64.6 lakh
Extension without contributions (letting the corpus compound without new deposits):
- ₹40.7 lakh growing at 7.1% for 5 years ≈ ₹57.1 lakh
- No new 80C benefit; no new deposits required
The extension with contributions is almost always superior — the additional 80C tax saving and continued compounding accelerate the corpus significantly.
Step 5: Understand the tax treatment
PPF enjoys EEE (Exempt-Exempt-Exempt) status — the most favourable tax classification in India:
- Contribution: deductible under Section 80C up to ₹1.5 lakh/year from taxable income
- Interest earned: completely exempt from income tax every year, with no upper limit
- Maturity proceeds: fully tax-free, including the full corpus and all accumulated interest
Compare this to an FD: FD interest is taxable at your slab rate every year. A 7.1% PPF return is equivalent to a pre-tax FD return of approximately 9.5% for someone in the 25% tax bracket, or 9.47% for someone in the 30% bracket. This tax equivalence makes PPF extremely competitive despite its seemingly moderate rate.
Step 6: Calculate the effective post-tax return
For comparison against taxable instruments:
PPF equivalent pre-tax return = PPF rate / (1 - your tax rate)
| Tax bracket | PPF equivalent pre-tax return |
|---|---|
| 5% | 7.47% |
| 10% | 7.89% |
| 20% | 8.88% |
| 30% | 10.14% |
For a person in the 30% bracket, a 7.1% PPF is equivalent to finding a 10.14% fully taxable investment — a threshold no bank FD currently reaches.
Common Mistakes to Avoid
Depositing after the 5th of the month. This is the most costly and most common mistake. On ₹1.5 lakh deposited on the 6th instead of the 1st, you lose one month's interest — around ₹890. Over 15 years of this habit, the cumulative loss exceeds ₹50,000 in foregone compounding.
Not making the minimum ₹500 contribution in a year. Missing even one year's minimum makes the account inactive, blocking loan and partial withdrawal facilities. Set up an annual reminder or auto-transfer in April.
Confusing PPF account year with financial year. Your PPF account matures 15 full financial years after the year it was opened, not 15 calendar years from the date of account opening. An account opened on 15 November 2010 matures on 1 April 2026 (at the end of FY 2025-26), not on 15 November 2025.
Withdrawing at maturity and reinvesting in a taxable instrument. The EEE advantage compounds over time. Extending PPF for another 5 years (instead of withdrawing and reinvesting in an FD) keeps the entire corpus in a tax-free environment, dramatically outperforming taxable alternatives on an after-tax basis.
Assuming the interest rate is fixed. The PPF rate is set quarterly by the government and can change. All projections in calculators are estimates based on the current rate. Plan conservatively by modelling scenarios at slightly lower rates (6.5%–6.8%) to stress-test your corpus against rate cuts.
Formula & Methodology
The complete PPF calculation used by the government is:
Monthly interest calculation:
Interest (month m) = Minimum balance between 5th and last day of month m × (Annual rate ÷ 12)
Annual interest credit (31 March):
Annual interest = Sum of monthly interest amounts for April–March
Opening balance next year:
New balance = Previous closing balance + Contributions made + Annual interest credited
This process repeats for 15 years (or longer with extensions). The PPF Calculator models this year-by-year, showing the cumulative balance, annual interest earned, and total interest across the full tenure.
Key Terms
- PPF — Public Provident Fund; 15-year government-backed savings scheme with EEE tax status
- EEE — Exempt-Exempt-Exempt; contribution, interest, and maturity are all exempt from income tax
- Section 80C — Income Tax Act provision allowing deduction of up to ₹1.5 lakh on qualifying investments including PPF
- Compound Interest — interest calculated on both the principal and previously earned interest, generating exponential growth
- CAGR — Compound Annual Growth Rate; used to express the annualised growth of the PPF corpus
- Corpus — total accumulated value of the PPF account at the point of maturity or withdrawal
- Small Savings Scheme — umbrella term for government-backed savings instruments including PPF, NSC, SSY, and SCSS