What this compound interest calculator works out
This is a free compound interest calculator that answers one question without ceremony: what does a starting amount, plus a contribution made regularly, become over a number of years? Type what you have today, what you can add and how often, the return you expect and how long the money can sit. The page prints the balance at the end, how much of it you paid in and how much of it is interest, then draws the same plan as a chart and a year-by-year table.
Compounding frequency is the setting most searches are really about. The menu opens on Monthly, so if you searched for a compound interest calculator monthly you are already on the right setting: a monthly compound interest calculator adds interest twelve times a year, and the effective rate under the fields shows what the same annual return is actually worth. Choose annually for an annual compound interest calculator on the same inputs, or daily for the daily compound interest calculator that a savings account quotes. The contribution has a menu of its own — monthly, weekly, biweekly or annual — and the amount you type is always for the period you picked.
Nothing here needs an account. The plan lives in the page address, so a link carries it and a reload restores it, and a scenario you save stays in your own browser. The full schedule downloads as a CSV for anyone who would rather check the arithmetic in a spreadsheet.
Withdrawals, fees and a step-up
A growth calculator usually only adds money, which is why compound interest calculator with withdrawals is a common search: a retirement plan, a drawdown or an account that pays for something all take money out as well as put it in. Open Advanced options and Take money out is a monthly figure taken from the balance on the last day of the month. If it is larger than the plan can carry, the page names the month the money runs out rather than charting a balance that cannot exist.
Two more levers sit in the same block. An annual fee is charged against the return before the money compounds, so the balance is what actually reaches the account. A yearly step-up raises the deposit by a percentage each year, the way a salary does. Set any of the three and the balance, the split between what you paid in and what interest added, the table and the chart all move together.
Compared with other compound interest calculators
You have probably used one of these already. The investor.gov compound interest calculator, the NerdWallet compound interest calculator, the Bankrate compound interest calculator and the Ramsey compound interest calculator all begin with the same three inputs — a starting amount, a contribution and a return — and the answer here begins in the same place. The reference plan on this page was checked against the compound interest calculator investor.gov publishes, and the two agree to the cent on the same assumptions: a constant return, deposits at the end of each period, and no tax.
What this page adds is everything beside that answer. Withdrawals, fees and a step-up share one view with the plain plan; a today's-money toggle takes inflation back off the balance; four plans compare on a single chart; and goal mode solves for the deposit you need instead of the balance you would reach. It is free, it runs in the browser, and it keeps nothing on a server.
The figures beside the tool belong to the reference plan, not to your plan. Change an input and the page works the whole thing out again, keeps the new plan in the address bar, and leaves the reference plan where it was.
Frequently Asked Questions
The answers below use this page's example rate, 7.0% a year compounded monthly, with nothing added and no tax or fees. Change the fields in the calculator above for your own figures.
How many years will $100,000 take to earn $50,000 in compound interest?
About 5 years and 10 months. At 7.0% a year compounded monthly, with nothing added along the way, $100,000 reaches $150,000 in that time — $50,000 of it interest. The plan assumes a steady return from the first month to the last.
How much will $750,000 be worth in 10 years?
$1,507,246.03, of which $757,246.03 is interest. That assumes 7.0% a year compounded monthly, with nothing added and nothing taken out. At this rate money doubles in about ten years, so a decade lands just over twice the $750,000 it started as.
Is it better to have simple or compound interest?
Compound interest, for anything longer than a year. Simple interest pays the same amount every year on the original sum. Compound interest pays on the original sum plus the interest already earned, so each year starts from a bigger base. Add the interest once a year and the two agree for the first year; add it monthly, as this page does by default, and compound is ahead from the first month. Either way the gap widens the longer the money stays. Borrowing works the same way, with the gap running against you.
What is the trick of compound interest?
The trick is that interest earns interest. Once a year's interest stays in the account, it joins the base that earns the next year's interest, so the growth feeds itself. Three things make it add up: leave the interest in, keep adding to the balance, and give it time. A small deposit made early does more than a larger one made late, because the early money has more years to compound.
What are the downsides of compound interest?
Compounding can work against you. Debt compounds the same way savings do, so an unpaid balance grows faster than the spending behind it. Fees and tax come off the return each year, and that smaller return compounds too. Inflation raises prices, so a balance can grow while what it buys does not — the today's-money toggle on this page takes 2.5% a year back off and shows the lower figure. The page also assumes a steady return, which no real investment promises.
What is a good compound interest rate?
There is no single good rate. What matters is the return left after inflation and fees, because that is what grows buying power — a headline rate that inflation cancels out leaves you level. This page's example is 7.0% a year, chosen as a round number to do arithmetic with, not as a forecast. An account with a fixed, guaranteed rate is usually quoted lower than the long-run return of a diversified share portfolio, which is not guaranteed and can fall. Use a rate you can defend over the horizon you are planning.
How much compound interest is earned by investing $20,000?
At 7.0% a year compounded monthly, $20,000 earns $20,193.23 over ten years and reaches $40,193.23. Left for twenty-five years instead, the same sum earns $94,508.36, because the later years compound on a much larger balance. The horizon is the bigger lever here: the same money at the same rate, very different interest.
What is the 3-year trick for calculating compound interest?
There is no separate three-year rule; the ordinary formula is quicker than a trick. For an annual rate r, three years of growth is the starting sum multiplied by (1 + r) three times. Written out, that adds exactly 3r + 3r² + r³ of the starting sum. The part most shortcuts drop is 3r² + r³, which is the interest earning interest. Three years is short enough to do by hand; past five or so, use the calculator, which compounds month by month rather than once a year.
What is the Rule of 72 in compound interest?
It estimates the doubling time. Divide 72 by the annual rate and the answer is roughly the number of years it takes for money to double. At 7.0% a year, 72 divided by the rate comes to a little over ten years, and this page's plan doubles in 10 years at monthly compounding. The rule is a good approximation at ordinary rates and drifts at very high ones.
How long will it take for $10,000 to double at 8.0% compound interest?
About 8 years and 9 months. At 8.0% a year compounded monthly, $10,000 reaches $20,000 in that time. The Rule of 72 gives nine years for this rate, so monthly compounding is a little quicker than the rule suggests. Compounded only once a year the money would take longer, because interest starts earning interest later.
Is there a quick way to calculate compound interest?
The Rule of 72 estimates doubling time: divide 72 by the annual rate and read the result as years. For a rough balance after t years, multiply the starting sum by (1 + r) once per year, or use the rule for a mental figure. For an exact answer use the formula A = P(1 + r/n)^(nt), where P is the starting sum, r the rate as a decimal, n the compounding periods in a year and t the number of years. The calculator above runs that arithmetic for you, contributions included.
What is a compound interest calculator?
A tool that answers one question: what does a sum become over time when the interest is left to compound? You enter a starting amount, a regular contribution and how often it is added, the annual return, how often interest compounds and how many years. It returns the final balance, how much of it you paid in and how much is interest, and usually draws the plan as a chart and a year-by-year table. The one on this page also handles withdrawals, fees, a yearly step-up, a goal to solve and up to four plans to compare.
How do you do compound interest on a calculator?
Use the compound interest formula, A = P(1 + r/n)^(nt). On a basic calculator: divide the annual rate by the number of compounding periods in a year, add 1, raise that result to the number of periods (the periods per year times the years), then multiply by the starting sum. For monthly compounding, enter the rate divided by twelve as a decimal, add 1, use the power key with the months, then multiply by the amount you start with. Regular contributions are a second run of the same calculation for each deposit, which is why the tool above is less error-prone than a hand sequence.
Does compound interest actually work?
Yes, as arithmetic. A balance earning a steady rate does grow faster as the interest is left in, and the example on this page was checked against investor.gov's calculator to the cent. What it cannot promise is the rate: real investments move up and down, fees and tax take a share, and inflation raises the prices you are saving against. Compounding rewards money that stays put for a long time, and the first years always look slow.
About this page
- Checked against
- investor.gov, $548,171.30
- Last updated
- 26 October 2026
- Sources
- SEC investor.gov
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Every figure on this page comes from one calculation, run by the same engine the tool uses. The reference plan is the plan the page opens on, and the numbers beside it were checked against investor.gov's own calculator.
This is general information, not financial advice. Investment returns vary, and a plan that assumes a steady return will not match a real one year by year.