Future Value Calculator

How to use the future value projection

This calculator estimates how much a starting balance plus equal recurring deposits may be worth after a specified number of compounding periods. It is a time-value-of-money model, not a forecast or promise of investment performance. The assumed rate is applied consistently in every period, while real returns, fees, taxes, inflation, and deposit amounts may vary.

What each input means

Number of periods (N) is the count of compounding intervals. A period can represent a year, month, quarter, or another interval, but every other input must use that same interval. Ten periods at 6% per period is not the same as ten years at a 6% annual rate compounded monthly. Use a whole number from 0 to 600. More periods generally increase future value when the rate and cash flows are positive, because both principal and earlier interest have more time to compound.

Starting amount (PV) is the balance available before the first period begins. It is required for a lump-sum projection but may be zero when modeling deposits only. A larger starting amount normally raises the final value proportionally. Avoid entering money that will not actually remain invested for the full horizon.

Interest rate (I/Y) per period is the growth rate applied during each interval. Enter 6% as 6 or 6%. A monthly model needs a monthly rate; an annual model needs an annual rate. A zero rate means there is no growth, and a negative rate models loss of value. Rates cannot be -100% or lower because that would eliminate or invert the balance in one period. Small rate changes can have a large effect over long horizons, so conservative scenario testing is usually more informative than relying on one optimistic assumption.

Periodic deposit (PMT) is the fixed amount added every period. It may be zero when projecting a starting lump sum only. Increasing the deposit raises both contributed principal and the interest that those deposits can earn. Do not enter a monthly deposit while treating N and the rate as annual values.

Deposit timing controls whether each PMT is made at the beginning or end of the period. Beginning-of-period deposits earn interest immediately and therefore produce a higher future value when the rate is positive. End-of-period deposits represent an ordinary annuity and match many payroll or month-end saving patterns.

How the calculation works

The starting amount compounds on its own, while the recurring deposits form an annuity. For an end-of-period deposit schedule, the model uses the ordinary-annuity formula. For beginning-of-period deposits, the annuity amount is multiplied by one additional growth factor because each payment compounds for one extra period.

Here, r is the rate per period and the timing factor is 1 for end-of-period deposits or (1 + r) for beginning-of-period deposits. When r is zero, the model uses the direct fallback FV = PV + PMT × N to avoid division by zero. The schedule independently rolls each period forward, which makes it easier to see how deposits and interest accumulate.

How to interpret the results

Future value is the projected closing balance after the last period. Present value (PV) discounts the projected future value back across the selected periods at the assumed rate; it represents the time-zero equivalent of the final amount under this model. Total periodic deposits is PMT multiplied by N. Total contributed combines the original balance and all deposits. Total interest is future value minus total contributed; it can be negative when the assumed rate is negative. Interest share shows how much of the final balance comes from growth rather than contributions. A high share can indicate strong compounding, but it can also reflect an aggressive rate assumption.

The breakdown chart uses the original starting principal, deposits, and interest so its components sum exactly to future value. The growth chart shows three series: closing balance, cumulative contributions, and cumulative interest. The projection table exposes the exact mechanics. Start balance is the amount entering a period; deposit is the period cash flow; interest is the amount earned or lost during that period; end balance is carried into the next row.

Scenario analysis and common mistakes

• Test a lower rate, a base rate, and a higher rate rather than treating one estimate as certain.
• Compare deposit timing only when it reflects a real cash-flow change; moving a deposit earlier is not free.
• Keep period units aligned. For a 6% nominal annual rate with monthly compounding, a simple approximation is 0.5% per month and 12 periods per year, though account conventions may differ.
• Remember that nominal future value does not show purchasing power. Inflation, taxes, fees, and volatility can materially reduce real outcomes.
• Use Reset to move to a neutral zero state, then build a fresh scenario without carrying forward stale assumptions.

For additional context, review the U.S. Securities and Exchange Commission’s compound interest calculator and its explanation of compound interest. The Federal Reserve Bank of St. Louis offers an accessible discussion of the time value of money, while the Consumer Financial Protection Bureau provides broader consumer money resources. These resources are educational and do not replace professional advice tailored to a specific financial situation.