THE NUMORIX GUIDE
How to use the Future Value Calculator
Last reviewed September 14, 2026
What this calculator does
The engine uses a monthly simulation.
Formula and method
The engine uses a monthly simulation. It converts annual rate to r = rate/100/12, starts with present value, charges interest on the current balance each month, then adds the monthly contribution. After periods x 12 months it returns future value, total contributions, total interest, and annual summary rows.
Variables and inputs
Enter Present Value, Annual Interest Rate, Years, and Monthly Contribution. The rate is annual, years is parsed as a whole number by the UI, and the contribution is deposited at the end of each simulated month after that month's interest calculation.
Worked example
For $1,000 at 12% for one year with a $100 monthly contribution, monthly rate is 0.12/12 = 0.01. The simulation ends at about $2,395.08; total contributions are $2,200 and modeled interest is about $195.08. Each $100 contribution is added after its month's interest.
How to interpret the result
Future value combines the starting balance, recurring deposits, and modeled growth. The result is higher when deposits arrive earlier or the return is higher, but the constant monthly-rate assumption should be treated as a scenario rather than a forecast.
Common mistakes to avoid
Enter an annual rate such as 7, not a monthly rate, and do not enter an annual contribution in the monthly field. Keep years as the intended number of full years. Check whether the real account credits interest monthly and when deposits become available.
Assumptions and limitations
The route uses nominal annual rate divided by 12, end-of-month contributions, whole-year horizons, and a constant return. It excludes fees, taxes, inflation, withdrawals, volatility, contribution limits, and negative-return periods unless the function is called outside the UI with such values.