Future value annuity due calculator

Input contract, formula, and response fields

Optionally set decimals to an integer from zero to eight for currency-style rounding of money outputs; the default is two. Money-like fields use half-up rounding once from the raw floating-point results so goldens stay byte-stable across runtimes. POST a JSON body with three required finite numbers: payment, the equal beginning-of-period cash amount, which must be strictly greater than zero; rate_percent, the interest rate per period expressed as a percent (five means five percent per period, not a decimal fraction), which must be greater than negative one hundred so that one plus r stays positive; and periods, a whole number of payments from one through one thousand two hundred. The engine forms the decimal rate r as rate_percent over one hundred, then computes the ordinary future value as payment times ((1+r) to the n minus one) over r when r is not zero, or payment times n when r is zero, and multiplies the ordinary result by (1+r) to obtain the annuity-due future value. total_deposited is payment times periods; interest_earned is future_value minus total_deposited; due_premium is future_value minus ordinary_future_value, which is the extra period of compounding. The response echoes payment (rounded), rate_percent, periods, rate_decimal, future_value, total_deposited, interest_earned, ordinary_future_value, due_premium, and a short formula string. Missing fields, empty strings, non-finite values, non-positive payment, non-integer or out-of-range periods, rate at or below negative one hundred, and out-of-range decimals fail with invalid_input and are not billed. Example: payment one thousand, rate_percent five, periods ten yields a due future value near thirteen thousand two hundred six point seven nine at two decimals, a larger ordinary counterpart near twelve thousand five hundred seventy-seven point eight nine, and a due premium equal to one period of interest on that ordinary balance.

Where a future value of annuity due API earns its keep

Classrooms and exam-prep generators need a deterministic oracle that distinguishes due from ordinary, handles a zero rate without dividing by zero, and rejects impossible bases instead of returning NaN. Product landing pages that rank for future value of annuity due calculator benefit from a free browser path that matches the paid automation path on the same pure module. Pair it with your own present-value or payment solver when the question is what to deposit, not what a known deposit stream will grow into. Retirement and payroll products often sweep a fixed contribution on the first calendar day of the month, which is an annuity due in monthly periods: feed the monthly payment, the monthly rate (annual nominal divided by twelve, entered as a percent), and the month count, and you get the projected balance plus the extra interest versus assuming end-of-month deposits. Landlords, insurers, and equipment lessors collect at the start of the term; converting a rent roll or premium schedule into a terminal value at a funding rate is the same identity, useful for comparing a prepaid stream with a lump-sum alternative. Sweep rate_percent or periods from your own code to build future-value tables; pin future_value and due_premium in tests; keep requests small. This tool does not amortize loans, discount a present value, or model changing payments or rates—only the fixed-rate future value of equal beginning-of-period cash flows.