SSY calculator

A negative yearly deposit is rejected with invalid_input instead of a silent negative corpus.

Input contract, response shape, and error behaviour

The scheme does not take deposits after year fifteen, and this contract refuses a count outside that window rather than silently clamping it. Example: one hundred fifty thousand yearly, eight point two percent, and fifteen deposit years is six remaining years, twenty-two lakh fifty thousand deposited, and a maturity at year twenty-one. Failed validation does not consume balance. POST a JSON body with three required finite numbers. yearly is the recurring SSY deposit in one currency, typically Indian rupees although the identity itself is unitless; aliases yearly_deposit, deposit, annual, pmt, and amount are accepted so worksheets can keep familiar column names, and the value must sit between zero and one trillion inclusive. A negative yearly deposit is rejected with invalid_input naming yearly; that is the contracted error and it is not billed, because an SSY account cannot receive a negative contribution. rate is the annual interest as a percent—eight point two means eight point two percent per year, not a decimal 0.082 unless you truly intend eight hundredths of a percent; aliases interest_rate and annual_rate map to the same field. rate must be from zero to one hundred inclusive so that one plus the annual rate stays positive and the power stays finite. years is the deposit window, an integer from one to fifteen inclusive; aliases deposit_years, tenure, and n are accepted. If yearly, rate, or years is missing, non-finite, or otherwise out of range, the task fails with invalid_input naming the field. Each field may arrive as a JSON number or a numeric string. On success the body echoes yearly, rate, and years, reports maturity_years as twenty-one and remaining_years as twenty-one minus years, and returns maturity_value, total_deposited, and interest_earned rounded half-up to two decimal places for stable currency-style goldens, plus a formula string restating the annuity-due closed form with idle compounding.

Where an SSY calculator earns its keep

Households in India use an SSY calculator when they are comparing a fifty-thousand-rupee yearly plan against the one-and-a-half-lakh ceiling over ten or fifteen deposit years and need one number for the maturity corpus plus the cash they will actually lock in. Post-office clerks, bank relationship managers, and goal-based planners need a deterministic oracle that rejects a negative yearly deposit instead of silently showing a negative corpus that a buggy form might treat as success. When you later need a monthly mutual-fund SIP, or a savings plan with an opening deposit beside recurring contributions, switch to those identities rather than stretching this three-field Sukanya Samriddhi contract. Product teams wire the same contract into onboarding demos so a user who types a yearly deposit, a notified percent, and a deposit-year count sees the identical maturity_value the API will later return in production tests. Keep requests small, pin rounded maturity_value and total_deposited in tests, and you get reproducible SSY figures for worksheets, LMS plugins, and edge workers without standing up a spreadsheet service of your own.