Future Value Calculator

What future value measures

Future value is the balance a sum of money reaches on a chosen date, assuming it grows at a steady rate. You start with $10,000, add $500 a month, assume 7 percent a year, and ask what the account holds 20 years from now. This calculator returns that number plus the three figures people usually want next: how much of it you paid in, what inflation leaves of it, and what monthly deposit a goal requires.

The idea is older than any calculator. A dollar today can be invested, so a dollar delivered a year from now is worth less than a dollar you hold now. Future value runs that logic forward. Present value is its mirror image and runs it backward, asking what a future sum is worth today.

Two habits make the result useful. Treat it as a range rather than a promise, because a steady 7 percent is an assumption and real investments do not repeat the same return every year. Then check whether the answer is in nominal dollars or in current dollars. A balance of $300,851 in 2046 and a balance with the buying power of $183,600 in 2026 are the same money, and only the second number tells you what the plan can buy.

If you know your deposit and want the number of months a target takes, the savings goal calculator answers that question. This page projects a balance forward to a date and works both directions from there.

The two formulas the calculator uses

Everything on this page comes from two equations. One grows the money you start with, the other grows the money you add along the way.

The monthly rate matters more than it looks. A quoted 7 percent compounded monthly is not 7 percent spread in a straight line: the monthly rate is 0.5833 percent, and twelve months of that compounding produce an effective 7.229 percent. The SEC compound interest calculator uses the same convention, which makes it a good second opinion when you compare a bank's advertised yield.

Deposits push the total past what a lump sum reaches alone. With no monthly deposit, $10,000 at 7 percent becomes $40,387.39 in 20 years. Add $500 a month and the same 20 years produce $300,850.72, because each deposit arrives with its own compounding clock.

Worked example: $10,000 plus $500 a month at 7 percent

Start with $10,000, add $500 at the end of every month, and assume 7 percent a year compounded monthly for 20 years.

• Monthly rate: 7 / 12 = 0.5833 percent, used as 0.005833
• Number of deposits: 20 x 12 = 240
• Lump sum growth: 10,000 x 1.005833²⁴⁰ = 40,387.39
• Deposit growth: 500 x (1.005833²⁴⁰ - 1) / 0.005833 = 260,463.33
• Future value: 40,387.39 + 260,463.33 = 300,850.72

You paid in $130,000, made of the $10,000 start and 240 deposits of $500. The remaining $170,850.72 is growth, which is 56.8 percent of the final balance.

Look at the gaps between rows. The first five years add $9,972.70 of growth. The last five add $113,880.10 on the same $30,000 of deposits, more than eleven times as much. That gap is the case for starting early: the early money is not earning a better rate, it is earning for longer.

What inflation does to the answer

A future balance buys less than the same number of dollars buys today, so a projection without an inflation adjustment flatters the plan. Divide the future value by (1 + inflation)^years to restate it in current dollars.

At 2.5 percent inflation, $300,850.72 in 2046 has the buying power of $183,600.45 today. That is a 39 percent cut to the headline number, and nothing went wrong to cause it. At 3 percent the real value is $166,573.75, and at 4 percent it is $137,304.34.

A rough rule is that 3 percent inflation halves buying power in about 24 years, since 72 / 3 = 24. Across a 20 year horizon the cut is closer to 45 percent than to half, which is why a long projection needs the nominal and real numbers side by side. The Bureau of Labor Statistics publishes the consumer price index these adjustments rest on, and its 20 year average is a better input than one year of grocery receipts.

One more wrinkle: the 7 percent in this example is a nominal return. With 2.5 percent inflation the real return is 4.39 percent, so the plan's buying power grows at that slower pace. Both statements describe the same plan, and neither one is wrong.

Compounding frequency, effective yield and doubling time

The quoted annual rate is not exactly the rate the money earns, because interest that lands mid-year starts earning too. Compounding more often lifts the effective annual rate, and the lift is small but not zero.

Moving from annual to monthly compounding adds $1,690.55 over 20 years on a $10,000 balance. Moving from monthly to daily adds $159.17. Each step buys less than the one before, which is why the gap between a 4.00 percent APY and a 4.07 percent APY rarely decides anything, while the gap between 4 percent and 6 percent decides plenty.

Doubling time follows from the same rate. At the effective 7.229 percent, money doubles in 9.93 years: ln(2) / ln(1.07229) = 9.93. Treat the quoted 7 percent as if it compounded once a year and the answer is 10.24 years, and the rule of 72 gives 72 / 7 = 10.29 years. All three land within five weeks of each other, which is why the rule survives. At 3 percent the exact answer is 23.45 years against the rule's 24, a gap of more than half a year.

The frequency choice also sets what a bank can advertise. A 7.00 percent APR compounded daily is a 7.25 percent APY, and a page that quotes the first number while paying the second is not lying, just choosing the friendlier label.

Working backward: the deposit a goal needs

The same equation runs in reverse. Give it a target, a date and a rate, and it returns the monthly deposit. To reach $1,000,000 in 30 years at 7 percent with no starting balance, the deposit is $819.69 a month. Across 360 months that is $295,088.98 paid in, so growth supplies the other $704,911.02.

Time moves the deposit more than the rate does. Going from 20 years to 30 years cuts the 7 percent deposit by 57 percent, from $1,919.66 to $819.69. Going from 5 percent to 8 percent across the same 30 years cuts it from $1,201.55 to $670.98, a 44 percent cut. A higher return helps, a longer runway helps more, and the runway is the part you control.

If the starting balance already grows past the goal on its own, the required deposit is zero and the page says so instead of printing a negative number. That case is common once a plan is halfway done and the growth is doing the work.

Deposits at the start of the month

The formula above assumes each deposit arrives at the end of the month. Many people are paid on the first, and money that goes in at the start earns one extra month of return on every deposit. The adjustment is a single factor: multiply the deposit part by (1 + i).

On the 20 year example, moving the deposits to the start of the month turns $260,463.33 of deposit growth into $261,982.70, an extra $1,519.37. That is 0.58 percent of the deposit total, earned by changing the transfer date and nothing else. On a 40 year plan the same shift is worth more, because each of the 480 deposits carries its extra month for longer.

Whether you capture it depends on the account. A payroll deduction that lands on payday captures it. A transfer scheduled for the 28th mostly does not, since it clears after most of the month's interest has posted. On a savings account paying 4 percent, the extra month is worth about 0.33 percent of each deposit, which is real money over decades and invisible over a month.

What the number leaves out

Four things sit outside the formula, and each one moves the real answer.

Taxes. Interest and dividends in a taxable account are taxed as they arrive, so the base that compounds is smaller than the calculator assumes. The IRS explains which interest is taxable in Topic 403. A tax-advantaged account changes the picture, and the same 7 percent can produce a different after-tax number in each.

Fees. A 0.75 percent annual fund fee is a 0.75 point cut to the return, not a rounding error. On the 20 year example, dropping the return from 7 percent to 6.25 percent removes about $28,000 from the final balance.

Volatility and sequence. A steady 7 percent and a real portfolio that returns minus 15 percent, plus 24 percent, then plus 3 percent can land in different places even when the average matches, because the order changes how much money is exposed at each point.

Your own behavior. Deposits stop during a layoff, get skipped for a car repair, or rise with a raise. A projection is a straight line and a life is not. Run the plan with a deposit you can keep for 12 months rather than the one you can keep for three.

For a single balance with no deposits, the compound interest calculator compares daily, monthly and annual compounding on the same starting sum. This page adds the deposit stream, the start-of-month option, the inflation-adjusted value and the reverse deposit calculation. Nothing here is investment advice or a forecast of returns.