Future Value Calculator

Compounds a present lump sum, optionally combined with a recurring monthly contribution, into a projected future value using a chosen interest rate, time horizon and compounding frequency.

Enter the present value, annual interest rate, number of years, a compounding frequency, and an optional monthly contribution. Leave the contribution at 0 to project the lump sum alone at the frequency you select.

A 10,000 present value at 5% annual interest over 10 years with monthly compounding and no contribution grows to about 16,470.09. Adding a 100 monthly contribution to the same inputs instead grows the balance to about 31,998.32, because the calculator switches to monthly compounding for both the lump sum and the contributions once a contribution is entered. Automated tests verify both figures.

Without a contribution: future value = present value × (1 + r)ⁿ, where r is the annual rate divided by the selected compounding frequency and n is frequency × years. With a contribution: future value = present value × (1 + r)ⁿ + contribution × [((1 + r)ⁿ − 1) ÷ r], using a monthly r and n regardless of the frequency selector, since monthly is the contribution's natural cadence.

Mixing a lump sum compounding, say, annually with contributions arriving monthly would require two different compounding schedules running at once. To keep the projection well-defined, entering any contribution switches the whole calculation to monthly compounding — the frequency selector then only matters when the contribution is 0.

The model assumes one constant rate for the entire period, contributions made in full every month with no gaps, and no withdrawals or fees. It does not model variable rates, taxes on investment gains, or inflation.

This is an educational estimate, not investment advice. The lump-sum and annuity future-value formulas were checked against U.S. SEC Investor.gov education materials. Reviewed September 2026. Calculation runs locally in the browser; Quiklio does not upload the entered values.