A worked example: ₹50,000 a year from age 2
Opening an SSY account for a girl aged 2 with ₹50,000 deposited every year results in ₹7,50,000 invested in total across the first 15 years. At the current 8.2% p.a. rate, compounded annually, the account earns ₹16,44,039.72 in interest by the time it matures — pushing the maturity amount to ₹23,94,039.72. The account matures in the year 2047, when the girl turns 23, even though deposits stopped six years earlier, in 2041.
The formula: 15 years of deposits, 21 years of compounding
The calculator simulates the account year by year. For each of the first 15 years, the annual deposit is added to the balance and the whole balance is then multiplied by (1 + 8.2%); for the remaining 6 years — years 16 through 21 — no deposit is added, but the balance keeps being multiplied by (1 + 8.2%) each year. Running that simulation with ₹1,00,000 a year from age 1 puts ₹15,00,000 in total deposits, which grows into ₹32,88,079.45 of interest and a maturity amount of ₹47,88,079.45.
A bigger contribution: ₹1,50,000 a year, the SSY annual cap
At the maximum permitted annual deposit of ₹1,50,000, opened at birth, total deposits over 15 years reach ₹22,50,000. Compounding through all 21 years brings total interest to ₹49,32,119.17, for a projected maturity amount of ₹71,82,119.17 when the girl turns 21.
Why six extra years of compounding matter so much
In every one of these examples, total interest earned is larger than the total amount deposited — for the ₹1,50,000-a-year case, ₹49,32,119.17 of interest against ₹22,50,000 invested. That happens because the largest balances in the account, built up over 15 years of deposits, then sit untouched and compounding for 6 more years with no withdrawals and no further contributions required — the exact stretch of time an SSY account is designed to let ride uninterrupted.