Published on August 5, 2026
Published by PraxisCalc, a Zeta Digilux Labs project
Future value has two parts: what you already hold compounding forward, and the deposits you keep adding. FV = P x (1 + r)^n + PMT x (((1 + r)^n - 1) / r), where r is the rate per period and n the number of periods. Starting with $10,000 and adding $200 a month at 6% produces $82,704 after 15 years.
Future value answers a simple but powerful question: if you save a certain amount regularly and earn a certain rate of return, how much will you actually have at the end? Unlike a single lump-sum future value calculation, savings-account future value combines two growth engines at once, the compounding of your starting balance and the compounding of every future contribution, each starting to grow from the moment it's deposited.
Total future value is the sum of two separate calculations: the future value of your initial lump sum (which compounds for the full duration), plus the future value of a series of regular contributions (where each contribution compounds for a progressively shorter period, since it's deposited later). This is why the formula looks more complex than simple compound interest, it's really two compounding calculations added together.
Whether you contribute at the beginning or end of each period (a monthly deposit made on the 1st versus the last day of the month, for example) creates a small but real difference in the final total, because beginning-of-period contributions get one extra compounding period each. Over many years and many contributions, this "annuity due" versus "ordinary annuity" distinction can add up to a noticeable difference, which is why it's worth confirming which convention your own bank or brokerage uses when comparing your real results to a projection.
Because every contribution's growth window shrinks the longer you wait to start, the same total amount contributed produces a meaningfully smaller final balance if spread over a shorter period versus a longer one. A saver who contributes for 30 years typically ends up with a substantially larger balance than one who contributes twice as much per month for only 15 years, purely because of how much longer the earlier contributions have had to compound.
Future value projections are only as good as the rate of return assumption behind them, and it's easy to overstate expected returns, especially for anything beyond a guaranteed savings account or CD. For growth-oriented projections (a brokerage account or retirement fund), use a conservative, historically-grounded rate rather than an optimistic best-case number, and revisit the projection periodically as actual returns come in, rather than treating a single projection as a fixed prediction.
The same formula can be run in reverse: instead of asking "what will I end up with," you can ask "what monthly contribution gets me to a specific target," which is exactly the calculation behind goal-based savings planning. Running both directions, forward from a contribution amount, and backward from a target, gives you a fuller picture of whether your current plan is realistic or needs adjustment.
Because both effects compound, a small change in either the assumed return or the time horizon has an outsized effect on the final projected balance, more than a linear reading of the numbers would suggest. Testing a projection at a slightly lower and slightly higher rate than your best estimate, rather than relying on a single point estimate, gives a more honest range of what to expect rather than false precision.
A future value projection built once at the start of a savings plan becomes less accurate the longer it goes unrevisited, since actual contributions, returns, and even the goal itself commonly shift over time. Recalculating annually, using actual account performance rather than the original assumption, keeps the projection a useful planning tool rather than a stale number from years earlier.
FV = P x (1 + r)^n for a single sum, plus PMT x (((1 + r)^n - 1) / r) for a stream of regular deposits. Add the two results. For monthly saving, divide the annual rate by 12 and count n in months.
Convert the rate and the term to months first. At 6% a year, r is 0.005 and 15 years is 180 months. The $10,000 opening balance grows to about $24,540 and the $200 monthly deposits add roughly $58,164, giving $82,704 in total.
In the example you deposit $10,000 up front plus $36,000 over 15 years, so $46,000 of the $82,704 is your own money and $36,704 is growth. The growth share rises sharply the longer the money is left alone.
Future value asks what today's money becomes later. Present value asks what a future amount is worth today, and it uses the same formula rearranged: PV = FV / (1 + r)^n. Use present value when comparing offers paid at different times.
The formula gives a nominal figure. To see what it will actually buy, discount the result by expected inflation. $82,704 in 15 years at 3% inflation has the buying power of about $53,100 today, which is the number worth planning against.
Match the rate to the account. A savings account or term deposit rate is knowable in advance, so use the quoted figure. For invested money the rate is an assumption, so run the calculation at two or three rates rather than trusting one.
Future value calculations combine the growth of what you've already saved with the growth of everything you'll contribute going forward, and starting early remains the single most powerful lever in the formula. For official investor education on compounding, see the SEC's explainer on the power of compounding. Project your own numbers with the Future Value of Savings Calculator.