Future Value Calculator

The example, in plain numbers

With the starting example ($10,000 to start, $200 a month, 20 years, a steady 7% a year and 3% inflation), the hypothetical ending value is about $144,573. You would have put in $58,000 ($10,000 plus 240 monthly contributions of $200), so about $86,573 is growth. In today’s dollars, that ending value would buy about what $80,046 buys now. At 5% or 9% instead of 7%, the same plan would end near $109,333 or $193,669.

What is compound growth?

Compound growth means your money earns a return, and then that return starts earning a return too. It is growth on top of growth. With a hypothetical $10,000 earning a steady 7% a year, the first year adds $700. The second year adds about $749, because now the 7% applies to $10,700, not just $10,000. Each year the snowball is a little bigger, so it picks up a little more.

That is why the gold part of the chart (growth) starts small and then takes over in later years. Early on, most of the balance is money you put in. Given enough time, growth can become the larger share.

Why time and steady contributions matter

Compounding needs time to do its work. Two hypothetical savers each put in $200 a month and earn the same steady 7% a year:

• Saver A starts 40 years before retiring: puts in $96,000 and ends with about $524,963.
• Saver B starts 10 years later, with 30 years to go: puts in $72,000 and ends with about $243,994.

Saver A put in only $24,000 more but ended with about $280,968 more, because the early money had an extra decade to compound. Steady contributions help in a second way: adding money on a schedule, in good markets and bad, builds the habit and keeps the snowball growing. Starting with a small amount still counts.

The Rule of 72, a quick shortcut

Divide 72 by a yearly growth rate to estimate how many years it takes money to double. At a hypothetical 7%, 72 ÷ 7 ≈ 10.3 years (the exact math gives about 10.2). It works in reverse for costs, too: at 3% inflation, prices roughly double in about 72 ÷ 3 = 24 years. It is a rough rule of thumb, most accurate for rates between about 6% and 10%.

How fees and inflation shrink growth

Fees come out every year, so their cost compounds too. Using $10,000 to start and $200 a month for 30 years: at a steady 7% the hypothetical ending value is about $325,159. If a 1% yearly fee lowers that to 6%, it is about $261,129, roughly $64,030 less. To see the effect of fees in this calculator, lower the return by the yearly fee. This calculator does not include fees or taxes unless you adjust the return yourself.

Inflation does not shrink the number on your statement, but it shrinks what that number can buy. At 3% a year, $100,000 twenty years from now would buy about what $55,368 buys today. That is why the calculator shows the result in today’s dollars. Taxes can also reduce growth, depending on the type of account.

How the math works (our assumptions)

• Monthly contributions: the yearly return is divided by 12 and compounded every month (a steady 7% a year becomes 7% ÷ 12 each month, which works out to about 7.23% over a full year). Each $200 is added at the end of the month.
• Yearly contributions: the return is compounded once a year, and each contribution is added at the end of the year.
• Starting amount: invested on day one and compounded the same way.
• Formula: ending value = start × (1 + i)ⁿ + contribution × [(1 + i)ⁿ − 1] ÷ i, where i is the return per period and n is the number of periods. This is the standard future value formula for an ordinary annuity.
• Today’s dollars: ending value ÷ (1 + inflation)^years.
• Not included: taxes, fees and expenses (unless you lower the return yourself), contribution limits, changes to how much you add, withdrawals, and the ups and downs of real markets.

Keep learning

• How to calculate investment returns, including real (after-inflation) returns and the effect of fees
• Glossary: future value, compound growth, compound interest, Rule of 72 and inflation
• Starting to invest and investing for retirement in Learn by Life Stage
• The Accumulation floor of the GRIP Financial House™, where Growth lives
• Investor Risk Self-Check: how much investment risk fits you

Official sources

• Investor.gov Compound Interest Calculator
• Investor.gov: Save and Invest
• Investor.gov: Mutual Fund and ETF Fees and Expenses
• FINRA Fund Analyzer

External links open official sites. Listing is not an endorsement.

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