Simple Investment Calculator

Simple investment calculator at a glance#

A simple investment calculator finds the future value of a one-time lump sum. It applies the growth formula future value equals present value times one plus the rate of return, raised to the number of periods: FV = PV (1 + r)^n. Each year the balance earns a return, and the next year earns a return on that larger balance.

Worked example: $1,000 invested at a 7% annual return for 10 years grows to $1,000 times 1.07^10, which is $1,967.15. Invest $5,000 at 6% for 20 years and it grows to $5,000 times 1.06^20, or $16,035.68. To calculate it by hand, raise one plus the decimal rate to the number of years, then multiply by the amount you invested.

Enter your starting amount, annual return and number of years in the calculator above for the exact future value. The result assumes a fixed return with no extra deposits or withdrawals, so fees, taxes and changing rates will shift the real figure.

The growth formula#

The future value of a lump sum is FV = PV (1 + r)^n, where PV is what you invest now, r is the annual return as a decimal, and n is the number of years. Each year earns a return on the whole balance, including returns already added, so the total climbs faster the longer you stay invested.

Adding regular contributions#

If you also add money on a schedule, the future value has two parts: the lump sum grows by (1 + r)^n, and the stream of contributions grows on top of it. The combined formula is FV = PV (1 + r)^n + C x [((1 + r)^n - 1) / r], where C is the contribution each period. Use this when you plan to keep paying into the account, such as a monthly deposit toward retirement.

Worked examples#

Mark, 30, wants $1 million by 40, a 10-year horizon. Starting with $200,000 and adding $250 a month at a 15% annual return, his balance reaches about $957,000, roughly $43,000 short of the goal, so he would need to raise his contribution or his timeline. Linda starts with $250,000 and wants $1.3 million in 15 years at an 8% return. Her starting balance grows to about $793,000 on its own, and to close the gap she needs to add about $1,465 a month.

Reading the result#

The projection assumes a single fixed return, which real markets do not deliver. To estimate buying power in current dollars, subtract your expected inflation rate from the return before you calculate, so an 8% return with 3% inflation gives a 5% real return. Taxes and fees also reduce the final figure, so treat the result as a planning estimate rather than a guaranteed amount.

FAQ#

How do I calculate the future value of an investment?#

Raise one plus the decimal rate to the number of years, then multiply by the amount invested: FV = PV (1 + r)^n. For $1,000 at 7% over 10 years, that is 1,000 x 1.07^10 = $1,967.15.

How do I find the starting amount I need?#

Divide your target by the growth factor: PV = FV / (1 + r)^n. To reach $10,000 in 8 years at 6%, you need 10,000 / 1.06^8 = about $6,274 today.

Does the calculator include compound interest?#

Yes. The (1 + r)^n term compounds each year's return onto the balance, so earnings build on earlier earnings rather than on the starting amount alone.

How should I set the rate of return?#

Use a figure that matches your investments and lean conservative. Past stock market returns have averaged in the high single digits, but any single year can be far higher or lower, so a lower estimate keeps the projection realistic.

How do I account for inflation?#

Subtract the expected inflation rate from your return to get a real rate, then run the calculation with that. This shows the result in current buying power instead of nominal dollars.

Can it handle regular contributions?#

Yes. Add your periodic deposit and the calculator grows both the starting balance and the contribution stream, which is how most retirement projections are built.