Starting balance plus regular contributions, compounded at the rate and frequency you choose.
Last reviewed September 2026
Sensible default. Modify inputs above to match your situation.
| Year | Balance | Total contributed | Interest earned |
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Enter a starting balance, an optional regular contribution, a rate, and how often interest compounds. We show the projected future balance, how much of it is your own money versus interest earned, and a year-by-year table so you can see the shape of the growth, not just the final number.
Compound interest means the interest you earn also earns interest, instead of only ever being calculated on your original balance. The standard formula for the future value of a lump sum is FV = P(1 + r/n)^(nt), where P is your starting principal, r is the annual interest rate written as a decimal, n is how many times per year interest compounds, and t is time in years. Add a regular contribution each period and its own growth stacks on top, using the standard formula for the future value of a series of equal deposits.
Leave this calculator on its $10,000 starting balance, no contribution, 7% annual rate, monthly compounding, and set the term to 10 years. That $10,000 grows to $20,096.61, doubling in a little over 10 years, which lines up with the "Rule of 72" shortcut of dividing 72 by the interest rate (72 / 7 is about 10.3 years).
Now try the opposite scenario: start with $0 and add $200 a month at the same 7% rate, compounded monthly, for 30 years. Total money actually deposited over that time is $200 x 12 x 30, or $72,000. The balance it grows into is $243,994.20, meaning interest alone accounts for roughly $172,000 of the total, more than double what was actually put in. Time in the market, not the size of the first deposit, is doing most of the work in that comparison.
People searching for a compound interest calculator with daily compounding often assume daily beats monthly by a wide margin. On $10,000 at 5% for 10 years with no added contributions, monthly compounding reaches about $16,470 and daily compounding reaches about $16,487, a difference of roughly $17 on ten years of growth. Rate and time move the outcome far more than compounding frequency does. Choose whichever frequency actually matches your account (most savings and investment accounts compound monthly) rather than assuming a more frequent setting meaningfully changes your outlook.
It projects growth before taxes. Where your money sits changes what you actually keep: a Roth IRA or Roth 401(k) can grow and come out tax-free under IRS rules if the withdrawal qualifies; a traditional 401(k) or IRA grows tax-deferred but is taxed as ordinary income on withdrawal; an ordinary taxable brokerage account may owe tax on dividends each year and on gains when you sell. This calculator does not model any of those tax treatments, inflation, account fees, or a return rate that changes year to year, it assumes one constant rate for the full period, which real markets never actually deliver in a straight line.
Future value of the starting balance uses FV = P(1 + r/n)^(nt). Future value of the periodic contribution uses the standard future-value-of-an-ordinary-annuity formula, PMT x [((1 + r/n)^(nt) - 1) / (r/n)], with each contribution treated as added at the end of its compounding period. Total interest earned is the projected balance minus the starting balance and every contribution added. The growth table steps through the same formula year by year rather than only showing the final balance.
FV = P(1 + r/n)^(nt), where P is your starting principal, r is the annual interest rate as a decimal, n is the number of times interest compounds per year, and t is time in years. If you add a regular contribution each period, its own growth adds PMT times the quantity (1 + r/n)^(nt) minus 1, divided by r/n. This calculator uses that exact formula and its output was checked against the U.S. Securities and Exchange Commission's own compound interest calculator.
The math is the same formula, it just adds an ongoing contribution term. Each contribution is treated as added once per compounding period, so with monthly compounding selected (the default here), your contribution amount is a normal monthly deposit. Switch the compounding frequency and the contribution follows that same schedule.
Less than most people expect. On $10,000 at 5% for 10 years with no added contributions, monthly compounding reaches about $16,470 and daily compounding reaches about $16,487, a difference of roughly $17. Rate and time move the outcome far more than compounding frequency does.
No. It projects pre-tax growth only. Money in a Roth account can grow and come out tax-free under IRS rules; money in a traditional 401(k) or IRA grows tax-deferred but is taxed on withdrawal; money in an ordinary taxable brokerage account may owe tax on dividends and on gains when sold. Which bucket your money sits in changes what you actually keep, this calculator does not model that difference.
Disclaimer. FigureNerd calculators are educational tools designed to support your decision-making. We are not licensed CPAs, attorneys, or financial planners. Results are directional and may help prompt consultation with a qualified professional. Tax, legal, and financial outcomes depend on individual circumstances. This calculator uses the standard compound interest formula and does not account for taxes on investment gains, inflation, account fees, or changes in contribution amounts over time. It is designed for educational illustration. Actual investment returns vary and are not guaranteed. Past performance of any asset class does not predict future results.