Future value answers a single question: if I put money in today and add to it every period at a fixed rate, what will it be worth at the end? This calculator compounds the starting amount and the periodic deposits, shows the interest earned on interest, and lays out every period so you can see where the growth comes from.

Inputs

End of period Beginning of period

Number of periods (N)1 to 1000 n

How many periods the money stays invested.

Starting amount (PV)At period 0 $

The one-off amount you start with.

Interest rate per period (I/Y)Percent, 6 means 6% %

Applied once every period.

Deposit per period (PMT)Negative to withdraw $

Added every period, before or after interest as chosen above.

Result

Future value —

Total deposits —

Total interest —

Schedule

Period Start Deposit Interest End

How the future value is calculated

Two things compound at once: the starting amount and the stream of deposits. With a per-period rate i and N periods:

FV = PV × (1 + i)^N + PMT × ((1 + i)^N − 1) / i

The first term is the starting amount growing on its own; the second is the annuity — each deposit earns for however many periods remain. When the rate is zero the formula collapses to PV + PMT × N, which is why the calculator handles that case separately instead of dividing by zero.

Worked example

Start with $1,000, deposit $100 at the end of each period, 6% per period, 10 periods:

Starting amount grows to 1000 × 1.06¹⁰ = $1,790.85
The deposits grow to 100 × (1.06¹⁰ − 1) / 0.06 = $1,318.08
Future value = $3,108.93; you put in $2,000, so $1,108.93 is interest

Period 1 shows the mechanism plainly: $1,000 start, $60 interest, $100 deposit, $1,160 end. By period 10 the interest alone is $170 — more than the deposit that period.

Beginning or end of period

Deposits made at the beginning of each period earn interest for that whole period, so the result is exactly the end-of-period value multiplied by (1 + i). On the example above that turns $3,108.93 into $3,295.46. The difference is small per year and large over decades, which is why the timing switch matters.

What this calculator leaves out

Inflation. The result is nominal. $3,108 in ten years buys less than $3,108 today.
Taxes. Interest is usually taxed as it accrues in a taxable account; the compounding shown here is pre-tax.
Variable rates. A single rate is assumed for the whole horizon. For changing rates, use a year-by-year model.
Risk. A fixed rate is a promise, not a forecast — the calculator projects, it does not predict.

Future value calculator FAQ

What is the difference between future value and compound interest?

Compound interest is the interest earned; future value is the whole balance at the end, including your deposits. This calculator reports both: total deposits, total interest, and the final balance.

Can I use negative numbers?

Yes for the deposit field — a negative amount models a regular withdrawal, and the balance will fall accordingly. The starting amount cannot be negative, and rates must stay above −100%.

How many periods can I enter?

Up to 1,000. That covers monthly compounding for over 80 years, which is beyond any realistic planning horizon.

Does a higher rate always mean a higher future value?

For a positive balance and positive deposits, yes. With withdrawals large enough to push the balance negative, the sign can flip — the schedule shows exactly where it happens.

Related tools

ROI Calculator — return on an investment in percentage terms.
Payback Period Calculator — when the cash flows recover the initial outlay.