Compound Interest Savings Calculator
See what your savings grow to with compound interest. Enter a starting balance, monthly deposit, rate and term, and see what an extra $50 a month buys.
Compound Interest Savings Calculator
What you are putting in
What's in the account today. Zero is fine: plenty of people are starting from nothing.
Added at the end of each month, after that month's interest is credited. This is a line in your monthly budget: it has to clear every month for the projection to hold.
What the account pays
The nominal annual rate. If your bank quotes an APY instead, choose Annually below and enter the APY here: that combination is what APY means.
The first three are deposit-account rates. 7% is a long-run market assumption for money you can leave alone for more than five years, and the balance can be down on the day you need it.
Whatever your account statement says. The difference between these four is real but small: the rate and the number of years move the answer far more.
How long it grows
Whole years, from 1 to 60.
Time is the lever that compounds on itself. Doubling the term does far more than chasing another half a percent on the rate.
At 0% the balance is exactly what you deposit and interest earned is $0.00. That is the honest answer for a cash jar or a checking account, and it is why this page iterates month by month instead of using the annuity formula, which divides by zero here.
Nothing to grow yet. Add a starting balance, a monthly deposit, or both.
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What another $50 a month buys
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Same starting balance, same rate, same term, with $50 more going in each month. Finding the $50 is the hard part: the monthly budget calculator sizes it against your real month, and the small daily purchases calculator is usually where it is already going.
Year by year
| Year | Balance | Paid in | Interest to date |
|---|
Each row is the balance at the end of that year, taken straight from the month-by-month run rather than from a separate formula.
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How this compound interest savings calculator works
Four inputs, one assumption set, and no hidden cleverness. Your deposit lands at the end
of each month, after that month's interest has already been credited, which is what
finance textbooks call an ordinary annuity. The annual rate you type is a nominal rate,
and it gets converted to an effective monthly rate using the compounding frequency you
pick: rMonthly = (1 + r / n) ^ (n / 12) - 1, where n is 1, 4, 12
or 365. Then the calculator walks forward one month at a time, crediting interest and
adding your deposit, for every month in the term.
There is a closed form for this. With monthly compounding the whole loop collapses to
FV = P(1 + r/n)^(nt) + PMT × [((1 + r/n)^(nt) − 1) / (r/n)], and you'll see
that formula on most pages covering this topic. It's correct, and it's not what this
page runs. The loop is the better engine here: annual, quarterly, monthly and
daily compounding all go through identical code, the year-by-year table falls out as a
side effect, and a 0% rate works instead of dividing by zero in that
r/n denominator.
A figure you can check the page against: $1,000 to start, $200 a month, 5% compounded monthly, 10 years. The effective monthly rate is exactly 0.05 / 12. After 120 months the balance is $32,703.47, of which $25,000.00 is money you deposited and $7,703.47 is interest. The closed form agrees to the cent, which is a useful sanity check on the loop even though the loop is what produces the number.
What another $50 a month actually buys you
Every other calculator makes you retype the deposit and remember the old answer. This one runs the projection twice and shows you the difference, because "is squeezing out another fifty worth it?" is the real question behind most visits to a page like this.
On the example above, moving from $200 to $250 a month adds $7,764.11 to the balance after 10 years. $6,000.00 of that is the extra deposits themselves, and $1,764.11 is interest those deposits earned on the way in. So the fifty dollars pays for itself and then some, and the longer the term, the more lopsided that split becomes. The size of the bonus depends far more on the years you leave it than on the rate you get.
The catch is that the $50 has to come from somewhere in the month. The monthly budget calculator will tell you whether it is actually there, and the small daily purchases cost calculator is usually where it has been going. If you would rather work backwards from a target instead of forwards from a deposit, the savings goal calculator solves for the monthly amount that hits a number by a date.
Rate, time and deposit: which lever actually matters
Time first. It's the only lever that compounds on itself, and the only one that costs nothing except starting sooner. Take $500 a month at 7% compounded annually with nothing to start: after 20 years the balance is $253,768.19, and $133,768.19 of that (52.7%) is interest rather than deposits. More than half the account is money you never earned at work, and it only gets there because the term is long enough for the early deposits to spend two decades growing.
The monthly deposit is second, and it is the lever you genuinely control month to month. Nobody can talk their bank into a better rate, but most people can find another $25 or $50. The savings rate calculator turns that deposit into a percentage of your pay if you want to benchmark it.
The rate is third, despite getting all the attention, because in the deposit-account range it just doesn't move much. Compounding frequency is fourth and barely counts: $10,000 at 8% over 20 years grows to roughly $46,610 compounded annually, $49,268 monthly and $49,522 daily. The whole annual-to-daily spread is about 6%, while the 8% rate is what got it there. Pick an account on its rate and treat the compounding schedule as a tiebreaker. And if the money might be needed inside a year or two, none of this applies: see the emergency fund calculator, because a compounding projection is the wrong tool for cash you cannot afford to have down on the day you need it.
Making the monthly deposit actually happen
A projection is only worth as much as the deposit landing every month. That is the part no calculator can do for you, and it's where most 10-year plans quietly fall apart: not in a dramatic month, just three or four skipped transfers that nobody noticed.
In Budget44 the deposit is a recurring transfer between two of your accounts on a monthly cadence. It shows up on the calendar as a projected entry and on the home Upcoming list before it is due, so a month you skip is visible rather than silent. A saving goal tracks the balance against a target with a progress ring, and net worth picks up the growing asset account automatically. Everything is entered by hand and stored on the device in ObjectBox as integer minor units, so totals stay exact to the cent: no account, no bank connection, no sync.
Got a number worth committing to? Download Budget44 and set the transfer up as a recurring line, so the projection on this page has something real behind it.
Frequently Asked Questions
Common questions about compound interest savings calculator
How does compound interest work on a savings account?
Your bank credits interest to the balance, and from that point on the interest earns interest too. That is the whole mechanism: each period starts from a slightly bigger number than the last one. This calculator applies one month of interest to the running balance, then adds your deposit, then repeats. Over a few years the effect is small. Over twenty or thirty it is the reason the final balance looks nothing like the money you actually paid in.
How much will my savings grow with compound interest?
It depends on all four inputs. Here is a case you can reproduce above: $1,000 to start, $200 a month, 5% compounded monthly, 10 years. That reaches $32,703.47. You deposited $25,000 of that, so $7,703.47 is interest you never had to earn at work. Stretch the same plan to 20 years and the interest share roughly doubles, because the balance doing the compounding is so much bigger in the second decade.
How often does interest compound, and does it actually matter?
Savings accounts and CDs vary: daily, monthly, quarterly and annually are all common. Daily edges out monthly, which edges out quarterly and annual, but the gap is small next to the rate and the term. The standard illustration: $10,000 at 8% over 20 years grows to roughly $46,610 compounded annually, $49,268 monthly and $49,522 daily. The whole annual-to-daily spread is about 6%, while the 8% rate is what turned $10,000 into $46,610 in the first place. Shop on the rate, treat compounding frequency as a tiebreaker.
Should I enter my APY or my interest rate?
This field wants the nominal annual rate, paired with the compounding frequency you select underneath it. If your bank only advertises an APY, select Annually and type the APY in: that pairing is the definition of APY, and the calculator will land on the same number the bank advertises. The assumptions line under the result shows the effective annual rate the tool is using, so you can check it against whatever your statement says.
What interest rate should I use?
Whatever your own account actually pays, not the rate you would like it to pay. For scale, and rates move: high-yield savings sat around 4% through 2026 while the national average savings rate was closer to 0.6%. The 7% chip is a long-run stock market assumption, not a savings rate, and the balance can be down on the day you need it. Money you might want inside five years does not belong there. The emergency fund calculator covers the money that has to stay liquid.
Does this calculator assume I deposit at the start or the end of the month?
End of the month, after interest for that month has been credited. That is an ordinary annuity, and it is the convention most savings calculators use. Depositing on the 1st instead would earn one extra month of interest on every single contribution, so treat the figure here as the slightly conservative one. If you do pay yourself on payday at the start of the month, your real balance should land a little above this projection rather than below it.
What difference does an extra $50 a month really make?
More than most people expect, and the panel on this page answers it without you retyping anything. Take the example above: $50 a month on top of $200, for 10 years at 5%, adds $7,764.11 to the final balance. $6,000 of that is deposits you made and $1,764.11 is interest those deposits earned on the way. The size of the bonus depends far more on the years left than on the rate, which is why starting the $50 now beats starting a better account later.
What if my savings account pays no interest at all?
Set the rate to 0. The tool still works and the answer is honest: your balance is exactly what you put in, and interest earned is $0.00. That is the correct model for a cash jar or a 0.01% checking account, and it is the reason this page iterates month by month instead of using the textbook annuity formula, which divides by zero at 0%. If you need a monthly amount rather than a projection, the savings goal calculator solves the same arithmetic backwards.