Future value calculator

What a single lump sum grows to with no further contributions — the nominal number, what it's worth in today's dollars, and how much the answer moves on the rate you assume.

How the math works

Future value is the compound interest formula with no contributions attached. A lump sum sits and grows.

Where FV is the future value, PV is the amount today, r is the annual rate, n is the number of times a year it compounds, and t is the number of years. With annual compounding, n is 1 and it collapses to the version most people know: FV = PV × (1 + r)^t. Switch the mode to present value and the calculator runs the same formula in reverse, discounting a future amount back to what it's worth today.

Compounding frequency barely moves the result at ordinary rates. On $1,000 at 6% over 10 years, monthly compounding beats annual by under $30. The rate and the horizon do the work; the compounding period is a rounding error.

Worked example

Take $10,000 invested once, with nothing added after, at the S&P 500's long-run real return of 7.0% for 30 years. Run the formula: $10,000 × 1.07³⁰.

The result is $76,123. Of that, $66,123 is growth and $10,000 is the original stake. The money grew more than sevenfold without a single extra dollar going in. That is the whole case for starting early and leaving it alone.

Note the rate we used. We chose the real return, 7.0%, not the nominal 10.2% — so the $76,123 is already in today's dollars. Most calculators run the nominal rate and print a bigger, more flattering number. The next section is why that number lies.

When this calculator is wrong

A future value is a projection dressed up as a fact, and it goes wrong in two directions that the mainstream calculators leave out.

The nominal number ignores inflation. Run the same $10,000 at the S&P 500's nominal return of 10.2% for 30 years and the calculator prints $184,267. That looks far better than $76,123. It isn't. Deflate it by the post-WWII average inflation rate of 3.3% and it's worth $69,573 in today's purchasing power — close to the real-return figure, because that's the same calculation done two ways. The nominal number tells you the digits on a future statement; the real number tells you what they buy. When a calculator shows you only the nominal figure, it is quietly counting inflation as growth.

The whole answer hinges on the rate you guessed. Hold the $10,000 and the 30 years fixed, and change only the assumed return:

• At 2.0% — the long-run real return on a 10-year Treasury — it grows to $18,114.
• At 7.0% — the real return on stocks — it grows to $76,123.
• At 10.2% — the nominal return on stocks — it grows to $184,267.

Same stake, same horizon, and the answers are more than $166,000 apart. The rate input is doing nearly all the work, and it's the one number in the calculator you can't actually know in advance. Which brings up the second thing worth stating plainly: past returns are a weak guide to the rate you'll get. As the empirical literature keeps finding, a fund's past performance has near-zero predictive power for its future relative performance. Treat the rate as a scenario, not a forecast, and run it more than once.

What to do with the result

Run the calculator twice: once at a real rate to see today's-dollars purchasing power, and once at a low rate as a floor. The gap between them is your uncertainty, and it's usually larger than people expect.

If your money is a lump sum you won't touch for years, the practical next question isn't the future value — it's the fee it grows under. Expense ratios above 0.50% almost never justify themselves: the average active fund charges 0.66% against 0.03% for a broad index, and over 30 years on a $10,000 stake that spread hands roughly $12,723 to the fund manager. Future value tells you what the market gives you. Fees decide how much of it you keep.

Common questions

What is future value?

Future value is what a sum of money is projected to be worth at a later date once it has earned a return. It's the mirror image of present value, which discounts a future amount back to today.

What rate should I use?

It depends on where the money sits. For a broad stock index, the long-run nominal return has averaged 10.2% and the real (inflation-adjusted) return about 7.0%. For a 10-year Treasury the real return has averaged 2.0%. Use the real rate if you want the answer in today's dollars.

Should I use the nominal or the real return?

Use the real return when you care what the money will buy — retirement spending, a house, tuition. Use the nominal return only when you're matching a nominal obligation, like a fixed loan balance. Running the nominal rate and forgetting to deflate it is the most common way a future value overstates itself.

Does this include monthly contributions?

No. This calculator is for a single lump sum with nothing added. If you're contributing every month, the compound interest calculator adds the ordinary-annuity term for the deposits.

Why does the compounding frequency barely change the answer?

Because at ordinary rates the difference between compounding once a year and daily is tiny — under $30 on $1,000 at 6% over 10 years. The rate and the number of years drive the result; the compounding period is close to a rounding error.