Compound interest with deposits kept independent of compounding. See APY, the crossover year, and all five frequencies compared.
Leave blank if you are only investing the starting amount.
Estimates only. Real returns vary, rates change, and this model ignores tax, fees and inflation.
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Most compound interest calculators hand you one number. This one splits that number into the money you paid in and the money the interest earned, shows the year your growth overtakes your deposits, and runs the same inputs at all five compounding frequencies so you can see what daily compounding is actually worth. Deposits are tracked separately from compounding, so a monthly deposit stays monthly whether the account compounds annually or daily.
Compound interest is interest paid on your interest. Simple interest pays only on the original amount; compound interest adds each period's interest to the balance, so the next period earns on a larger base. That difference is invisible over a year and decisive over a decade. Two frequencies matter and they are not the same thing: how often the account compounds (n) and how often you deposit (m). A deposit starts earning the moment it lands, at that period's effective rate, which is why this calculator evaluates deposits at (1 + r/n)^(n/m) − 1 rather than at the compounding rate.
Compound Interest Formula (with deposits)
Most savings accounts compound daily and credit monthly. Model daily compounding with monthly deposits to see the real end balance.
A lump sum plus a fixed monthly contribution over a long horizon — the shape most retirement saving actually takes.
Compare a CD's nominal rate against its APY, and against the same money compounded more often elsewhere.
Thirty-year horizons are where the crossover year lands well before the end, and where deposit timing starts to matter.
The zero-interest preset gives the baseline: the same deposits with no growth at all, so the compounding effect is the difference between the two.
Change the compounding frequency and your monthly deposit stays monthly. Many calculators quietly pay it n times a year, which inflates a daily-compounding answer by a factor of thirty.
The same money at annual, semi-annual, quarterly, monthly and daily compounding, with the difference against annual in dollars — the honest answer to how much frequency is worth.
The year your interest earned first exceeds everything you have paid in. It is the single clearest measure of whether compounding is doing the work yet.
An annuity-due option for people who invest on payday rather than at month end, worth one extra period of growth on every deposit.
The effective annual rate is computed the way Regulation DD defines it, so the figure matches what a bank must publish.
Less than most people expect. On $10,000 at 6% with $500 a month for ten years, daily compounding produces about $100,225 against $99,145 compounded annually — roughly $1,079, or about 1% more, over a decade. Frequency is real but small; the rate and the time horizon dominate. The frequency table on this page shows the exact gap for your own numbers.
The nominal rate is the headline figure. APY (annual percentage yield) folds in the compounding: at 6% nominal compounded daily, the APY is 6.1831%. APY is what a US bank is required to publish under Regulation DD precisely because it makes accounts with different compounding schedules comparable. Enter the nominal rate here and the calculator reports the APY.
Yes, by exactly one period of growth on every deposit. A start-of-period deposit (an annuity-due) is worth the end-of-period result multiplied by (1 + i). Over thirty years of monthly deposits at 7%, that is a difference of several thousand dollars for no extra money invested — it is purely a matter of when the money lands.
The first year in which the interest you have earned is worth more than everything you have paid in, principal and deposits together. Before it, your balance is mostly your own money; after it, it is mostly growth. For a typical index-fund scenario — $10,000 plus $500 a month at 7% — the crossover falls around year 18.
A shortcut for doubling time: divide 72 by the annual rate. At 6% money doubles in about 12 years. It is an approximation of the logarithmic answer and is most accurate near 8%; this calculator computes the exact figure instead.
No. The balance shown is nominal and pre-tax. Interest in a taxable account is usually taxed as ordinary income in the year it is credited, and inflation erodes what the final figure buys. For a rough real return, subtract the inflation rate from your nominal rate before entering it.