Compound interest calculator 2026
This compound interest calculator projects the balance of a lump sum plus regular deposits or withdrawals at a fixed annual rate, with nine compounding choices from annual to continuous. It shows the APY using the Regulation DD formula, the balance in start-date dollars with US inflation at 3.7 percent (the BLS CPI-U change for the 12 months to September 2026), and a range of results above and below your rate. As an example, $10,000 plus $200 a month at 7 percent compounded monthly grows to $54,713.58 after 10 years.
Calculate compound interest
Results update as you change any field. Press Calculate to see messages for any field that needs fixing.
Results
Future balance
-
Net amount put in
-
Total interest earned
-
Initial investment
-
Additional contributions
-
Balance in start-date dollars
-
Annual percentage yield (APY)
-
Where the final balance comes from
Results across the rate variance range
| Annual rate | Future balance | Interest earned |
|---|
Growth over time: stacked area chart
Grey is net money put in, blue is interest. Dashed lines are the low and high rates from the variance range.
Year-by-year breakdown
Balance at the end of each year. The last row covers the full period, including any part year.
| Period | Net put in | Interest earned | End balance | In start-date dollars |
|---|
How this calculator works
For a single deposit with no further contributions, the future value is:
A = P × (1 + r/n)(n × t)
In words: one plus r divided by n, raised to the power n times t, multiplied by P.
Here P is the starting amount, r the annual rate as a decimal, n the number of compounding periods a year and t the number of years (Calculator.net gives the same formula). With continuous compounding the formula becomes A = P × e(r × t), where e is about 2.71828.
Regular deposits each compound for a different length of time, so the calculator works period by period. Between two contributions the balance grows by one plus r/n raised to the power n/m, where m is the number of contributions a year, and then the contribution is added:
Balancenext = Balance × (1 + r/n)(n/m) + Contribution
This is the equivalent-rate method CalculatorSoup describes for payments and compounding on different schedules. When n and m match, the exponent is 1. When they differ, for example annual compounding with monthly deposits, the monthly growth is 1.07(1/12) − 1 = 0.5654 percent at 7 percent, not 7/12 = 0.5833 percent. With continuous compounding the factor is e(r/m). For beginning-of-period deposits, the deposit goes in first and then the balance grows. If the duration ends partway through a contribution period, interest is added for the part-period, and an end-of-period deposit for that unfinished period is not made.
APY and the Regulation DD formula
The APY figure in the results is the yield over one year after compounding:
APY = (1 + r/n)n − 1 (continuous: er − 1)
This is the general formula in Appendix A of Regulation DD, 12 CFR 1030, APY = 100 × [(1 + Interest/Principal)(365/Days in term) − 1], applied to a 365-day term. Banks in the US must quote savings yields this way, so the APY here can be compared directly with a bank's stated APY. At 6 percent the APY is 6.00000 percent compounded annually, 6.16778 percent monthly and 6.18313 percent daily.
Inflation adjustment
Balance in start-date dollars = future balance ÷ (1 + i)t, where i is the inflation rate. The default of 3.7 percent is the 12-month change in the CPI-U to September 2026 from the Bureau of Labor Statistics, released October 14, 2026. The next CPI release is due November 10, 2026, and we update the default after it.
Worked example
The calculator opens with $10,000 to start, $200 at the end of every month, 7 percent compounded monthly, 10 years, inflation 3.7 percent and a variance range of 1. You put in $34,000 ($10,000 plus 120 deposits of $200). The future balance is $54,713.58, so interest is $20,713.58. The APY is 7.22901 percent. In start-date dollars the balance is $38,045.87, which is $54,713.58 ÷ 1.03710. At 6 percent the balance would be $50,969.84 and at 8 percent $58,785.61.
Two changes show how the timing and compounding inputs work. Moving the deposits to the beginning of each month raises the balance to $54,915.51. Switching to annual compounding with the same monthly deposits lowers it to $53,881.86. A withdrawal example: $300,000 at 5 percent compounded monthly with -2000 a month pays 235 full withdrawals; the money runs out at month 236, during year 20, after paying out $471,778.60 in total.
What each input means
- Initial investment: the balance on day one. Enter 0 if you start from nothing.
- Regular contribution or withdrawal: the amount added each period. A negative number is taken out instead, as on the SEC Investor.gov compound interest calculator.
- Contribution frequency: annually, quarterly, monthly, semimonthly (24), biweekly (26), weekly (52) or daily (365).
- Deposit timing: end of each period (an ordinary annuity) or beginning (an annuity due).
- Annual interest rate: the nominal rate, before compounding. The calculator accepts 0 to 100.
- Compound frequency: how often interest is credited, from annually to continuously.
- Investment duration: years or months. A part year is handled with a part-period of interest.
- Annual increase in contribution: raises the regular amount each year, compounding (3 percent turns $100 into $103, then $106.09).
- Inflation rate: used only for the start-date dollars column and figure.
- Rate variance range: shows the same plan at two more rates, below and above yours.
Limitations
- The rate is fixed for the whole period. Investment returns vary and can be negative.
- No taxes, account fees or fund expenses are taken out.
- Interest is credited without rounding to the cent, so a bank statement can differ by a few cents.
- Days are counted as 365 a year and weeks as 52, so weekly and daily plans differ slightly from calendar-exact schedules.
- The inflation figure is one past 12-month rate, applied to every year.
- Results are projections from your inputs, not a promise of future returns.
Compound interest calculator FAQs
How does this compound interest calculator work?
It builds the balance one contribution period at a time. In each period the balance grows by (1 + r/n) raised to the power n/m, where r is the annual rate, n is the number of times interest compounds each year and m is the number of contributions each year. The contribution is added at the end of the period, or at the start if you choose beginning of period. With no contributions this gives the same answer as A = P(1 + r/n) raised to the power nt.
What is the difference between APR and APY?
The interest rate you type is a nominal annual rate. APY, the annual percentage yield, is the return over one year once compounding is counted. Regulation DD, the federal rule for deposit account disclosures, defines APY in Appendix A of 12 CFR 1030. For a one-year term with interest compounded n times, that formula works out to (1 + r/n) raised to the power n, minus 1. A 6 percent rate compounded monthly is an APY of 6.16778 percent.
Does compounding frequency make a big difference?
Less than most people expect. At 7 percent with $10,000 to start and $200 a month for 10 years, the balance is $53,881.86 with annual compounding, $54,713.58 with monthly compounding and $54,793.49 with continuous compounding. The rate, the amount you add and the number of years move the result far more.
Should I choose beginning or end of period for my deposits?
Pick the one that matches when money actually reaches the account. A deposit made at the start of each month earns one extra month of interest compared with one made at the end. With the default inputs on this page the beginning-of-period balance is $54,915.51 against $54,713.58 at the end of each period. Most savings plans funded from a paycheck sit closer to the end-of-period case.
How do I model withdrawals?
Enter the regular amount as a negative number, for example -1500 for $1,500 taken out each month. The calculator subtracts it on the same schedule and still pays interest on what is left. If the balance runs out, later withdrawals are cut to zero and a warning shows the year it happens. The annual increase field then raises the withdrawal each year, which is a simple way to keep spending in line with prices.
What does the inflation-adjusted value mean?
It is the future balance expressed in dollars with the buying power of the start date. The calculator divides the balance by (1 + i) raised to the number of years, where i is the inflation rate you enter. The default is 3.7 percent, the 12-month change in the consumer price index for all urban consumers to September 2026 published by the Bureau of Labor Statistics on October 14, 2026. Long-run inflation can be higher or lower, so try a few values.
What is the rate variance range?
It reruns the same plan at your rate minus the range and plus the range, the approach the SEC uses on the Investor.gov compound interest calculator. With 7 percent and a range of 1, you see results at 6, 7 and 8 percent in a table and as dashed lines on the chart. A low rate below zero is set to zero.
Can I use this for stocks or index funds?
Only as a rough guide. The calculator assumes one fixed rate every year. Stock and fund returns change from year to year and can be negative, and funds charge fees. Use the rate variance range to see a spread of outcomes, and treat the result as an illustration, not a forecast.
Are taxes included?
No. Interest is added in full each period with no tax or fees taken out. Interest on a taxable savings account or bond is generally taxed each year, which lowers the growth rate, while tax-advantaged retirement accounts follow different rules. Lower the rate you enter to approximate an after-tax return.
How we check this calculator
On November 6, 2026 we read the calculator code and ran nine test cases against an independent Python model and the live page: a lump sum, matched monthly deposits, beginning-of-period deposits, annual compounding with monthly deposits, weekly deposits with daily compounding, a 3 percent annual increase, an 18-month term with monthly and with annual compounding, and APY at three frequencies. Every result matched to the cent. The growth step was already correct; the earlier version said it reported an effective annual rate but showed none, and added a pro-rated deposit at the end of a part period. Both are fixed. The inflation default is reviewed after each monthly CPI release.
Revision history: November 6, 2026, added beginning-of-period deposits, withdrawals, APY with the Regulation DD formula, inflation adjustment, rate variance range, semimonthly, biweekly, weekly and continuous compounding, worked example and FAQ; previous edition September 21, 2026.
Related: SIP calculator, interest rate calculator, inflation calculator, pension calculator, Social Security calculator, credit card payoff calculator, Treasury bond rates, ETFs to watch in 2026, all calculators.
Sources: CFPB, Regulation DD Appendix A; BLS, Consumer Price Index news release; SEC Investor.gov, compound interest calculator; Calculator.net, compound interest formulas; CalculatorSoup, future value with mismatched periods.
This calculator gives an educational estimate from the figures you enter, using the formulas cited above as of November 6, 2026. It is not investment, tax or financial advice. See our disclaimer.
FintechZoom.Live covers stocks, crypto, commodities, forex and bonds with live TradingView charts and dated, sourced analysis. Browse the newest market articles on our blog.
Curated Editorial Insights Across FintechZoom’s Core Verticals: Thought-provoking analysis in Markets, Business Strategy, Crypto Innovation, Personal Finance, Economic Policy, and Lifestyle Wealth, designed to challenge conventional thinking, deepen financial literacy, and empower readers to make smarter, forward-looking decisions.
