What does $10,000 grow to at 5% in 10 years?

Leaving one deposit alone for a decade

A single deposit is the purest form of the compound interest question. There are no monthly contributions to muddy the picture, so everything the balance gains over the ten years is growth on the original $10,000 and on the growth already added to it. That makes this page useful for a very common situation: money that arrived all at once, such as a bonus, an inheritance, the proceeds of a sale or savings moved out of a checking account, and the question of what it could become if you simply left it.

The calculator handles it the same way it handles every input on the main page. The monthly contribution is zero, so at the start of each month nothing is added, and the whole balance then earns one month of growth at 5% divided by twelve. After twelve of those steps the year closes, the year-by-year table records the balance, and the next year starts from that larger number. Because nothing new arrives, the contributions line in the chart stays flat at $10,000 for the entire decade, and the area above it is growth alone. The curve bends upward only gently over a period this short at this rate, which is exactly what makes it a useful contrast with the long, deposit-heavy examples elsewhere on the site.

Five percent is a deliberately moderate figure. It sits in the range people use when they think about a balanced investment fund over the long run, or a good savings rate when rates are high, and it is lower than the return the main calculator assumes. If the account you have in mind pays a different rate, change it and the whole page recomputes. The result is before tax, fees and inflation, and a real account rarely earns the same return every year, so read the headline as a precise what-if rather than a forecast. The rule-of-72 callout under the result shows how long this rate takes to double a single deposit, both by the shortcut and exactly.

How much compounding adds over only ten years

The comparison with simple interest is especially telling here. With simple interest the $10,000 would earn the same 5% of the original amount every year and nothing on top. Compounding pulls ahead of that, but on these inputs the extra it adds is less than a quarter of the gain; most of the gain is the plain 5% a year on the original deposit. Time is what changes that balance. Raise the years and watch the compounding-versus-simple figure on the result, or pin this result first so the comparison card shows the two side by side.

Compound interest compared with simple interest

Simple interest pays a return only on the money you put in, never on earlier returns. The calculator works out that alternative for the same deposits so you can see what compounding itself adds. Your initial amount earns the stated rate once per year for the whole period, and each monthly deposit earns the same rate for the months it has been in the account, with nothing reinvested. The card that compares the two shows the simple-interest total and the difference between it and the compounded balance. Early on the two lines sit almost on top of each other, because the returns that could earn returns are still small. The gap opens slowly and then quickly, and in the chart it is the widening space between the curve and the straight line of contributions. That gap is the reason time in the account matters so much: most of it appears in the last third of a long period.

The rule of 72 and its exact form

The rule of 72 is a mental shortcut for doubling time: divide 72 by the annual return in percent and you get roughly how many years it takes for money to double with nothing added. At 6% the rule says 12 years. The exact answer comes from logarithms, the natural log of two divided by the natural log of one plus the rate, which at 6% gives about 11.9 years. At 9% the rule says 8 years and the exact figure is very close to it. The shortcut works because it is tuned for the middle of the range people usually use, and it drifts at very low or very high rates. The callout on the result shows both numbers for the rate you enter, so you can see how close the shortcut is. Doubling time applies to a single lump sum. With monthly deposits the balance grows faster than that, because new money keeps arriving.

What this calculator assumes, and what it leaves out

Every figure on this page comes from the same few assumptions. Deposits are made at the start of each month and never skipped. The annual return is constant for the whole period. Nothing is withdrawn. The results are before tax and before fees, and they are in future dollars, not adjusted for inflation, so a large balance decades from now will buy less than the same number would today. Taxes on interest and gains depend on the account type and where you live, and fund or platform fees reduce the return you actually keep, so a real account will usually end below the figure shown here. If you want a rough sense of the effect of fees, lower the annual return by the yearly cost you pay and run the numbers again. To think in today's money instead, enter a return that is already reduced by the inflation you expect. Neither adjustment is exact, but both move the projection closer to what you are likely to see.