The quick math

Money that earns a return every year grows on its own gains, which is called compounding. For a single deposit, the formula is:

Compounding speeds up over time. In the first year at 7%, $10,000 earns $700. In the tenth year, it earns about $1,287, because the balance it is working on has grown. By the end, $9,672 of the total is growth, almost as much as the original deposit.

A quick way to estimate is the rule of 72: divide 72 by the yearly return to see how many years it takes money to double. At 7%, that is about 10.3 years, which is why $10,000 comes close to $20,000 in a decade.

$10,000 after 10 years at different rates

The rate is everything. Here is the same $10,000 left alone for 10 years:

The gap between 0.38% and 4% is not a rounding error. The FDIC reported a national average savings rate of 0.38% for August 2026, while several high-yield savings accounts were paying around 4% APY. On $10,000, that is roughly $38 versus $400 in the first year alone.

What kind of return is realistic?

The right rate to plan with depends on where the money sits and how much risk you can accept:

• Regular savings accounts often pay well under 1%. Safe and easy to reach, but the money barely grows.
• High-yield savings accounts, CDs and Treasury bills have recently paid around 4%. Rates move with the economy and can fall. Savings and CDs at FDIC-insured banks are insured up to the legal limits.
• Diversified stock funds have historically earned more over long periods, but with large swings. Some years they lose value, and past returns do not guarantee future results.
• A mix of stocks and bonds usually falls between the two, with smaller swings than stocks alone.

Because investment returns are uncertain, many people plan with a conservative rate, such as 5% to 7% for a long-term stock-heavy portfolio, and check a lower rate to see the downside. For money you will need within a few years, a savings account or CD rate is the safer assumption.

Adding monthly deposits

A starting balance is only half the story. Regular contributions often end up larger than the original deposit. Here is $10,000 plus a monthly deposit for 10 years:

With $200 a month at 7%, you put in $34,000 in total and end with about $53,882, so roughly $19,882 comes from growth. Finding an extra $100 or $200 a month often matters as much as finding a better rate. A pay raise is a natural place to find it: saving part of each raise increases deposits without cutting your current spending.

Time matters even more than rate

Here is $10,000 at 7% a year, with no extra deposits, left for different lengths of time:

1. After 5 years$14,026
2. After 10 years$19,672
3. After 15 years$27,590
4. After 20 years$38,697
5. After 30 years$76,123

Growth in the second decade is bigger than in the first, and the third decade is bigger still. Going from 20 to 30 years adds more than $37,000, almost four times the original deposit. That is why starting early is so powerful, even with modest amounts.

Don't forget inflation and taxes

A bigger balance does not always mean more buying power. If prices rise 3% a year, something that costs $10,000 today would cost about $13,439 in 10 years. Here is what each balance is worth in today's dollars at 3% inflation:

Money in a low-rate account actually loses more than a fifth of its buying power over 10 years. Taxes also matter. Interest from savings accounts and CDs is usually taxed as ordinary income each year, and investment gains may be taxed when you sell. Tax-advantaged accounts such as a 401(k) or IRA can delay or reduce those taxes, which lets more of the money keep compounding.

Before you invest $10,000

1. Pay off high-interest debt first. Paying off a credit card at 22% is like earning a guaranteed 22% return. Our snowball vs. avalanche guide shows how to plan it.
2. Keep an emergency fund. Many people hold three to six months of expenses in savings before investing for the long term.
3. Match the account to the goal. Use savings or CDs for money you need soon, and long-term investments for goals many years away.
4. Keep fees low. A 1% yearly fee on a 7% return leaves 6%, and over 10 years that turns $19,672 into about $17,908.
5. Automate monthly deposits. Small, regular contributions add up faster than most people expect.

Frequently asked questions

Sources and how we calculated

All figures use yearly compounding, with monthly deposits added at the end of each month using the equivalent monthly rate. Values are rounded to the nearest dollar and ignore taxes and fees. The national average savings rate comes from the FDIC's National Rates and Rate Caps. To learn more about deposit insurance, see the FDIC's deposit insurance page, and for investing basics, the SEC's Investor.gov.