16 September 2026

How Sukanya Samriddhi interest is actually calculated (and why your passbook looks low)

A worked example of the month-by-month calculation the post office uses, the annual credit on 31 March, and the difference between the passbook balance and what the account has really earned.

Most online SSY calculators assume a yearly deposit at the start of the year and apply today’s rate to the whole term. The post office does something more specific. Here is the real method, with a worked example.

The three rules

1. Monthly calculation on the lowest balance between the 5th and the month-end. For each month, take the smallest balance the account held from the 5th to the last day, and compute interest as balance × rate ÷ 12.
2. The rate for a month is the rate in force that quarter. The Ministry of Finance notifies rates every quarter; the current one is on our rates page.
3. Interest is credited once a year, on 31 March, rounded to the rupee, and joins the balance for the next year’s calculation.

A worked example

An account is opened on 5 April 2023 with ₹1,50,000. The rate was 8.0% for April–December 2023 and 8.2% from January 2024.

• April to December: 9 months × ₹1,50,000 × 8.0% ÷ 12 = ₹9,000
• January to March: 3 months × ₹1,50,000 × 8.2% ÷ 12 = ₹3,075
• Credited on 31 March 2024: ₹12,075. New balance ₹1,62,075.

Another ₹1,50,000 on 5 April 2024. Rate 8.2% all year:

• 12 months × ₹3,12,075 × 8.2% ÷ 12 = ₹25,590.15
• Credited on 31 March 2025: ₹25,590. New balance ₹3,37,665.

Had the second deposit gone in on 8 April instead of the 5th, April would have been calculated on ₹1,62,075, not ₹3,12,075 — ₹1,025 less at year-end, and less to compound for the next seventeen years.

Why the passbook looks low

The passbook shows the balance as of the last 31 March. In September, it does not include the six months of interest the account has earned since — that interest exists, it just has not been credited yet. Sukanya Tracker shows both: the credited balance the passbook will print, and the accrued interest on top, so the number you see is what the account is really worth today.

Checking your own passbook

Take the interest printed for the last financial year and compare it to what the rules give. If they disagree, the usual reasons are:

• a deposit made after the 5th (starts earning a month later than you assumed);
• a rate change part-way through the year;
• a deposit that crossed the ₹1.5 lakh cap and was returned.

The app has a reconcile box for exactly this: type the passbook’s interest for a year and it tells you whether it matches, and if not, by how much. Get the app →