What is saving monthly worth?
Enough that the boring answer is worth checking. Small monthly amounts compound into numbers most people guess low by an order of magnitude.
This free calculator takes one monthly amount and shows what it becomes after one, ten and thirty years, three different ways: invested and compounding at an assumed 7% return, held as cash with no growth at all, or put against a debt where the payoff is the interest you stop paying. Saving $150 a month and investing it comes to about $1,859 after a year, about $25,963 after ten years and about $182,996 after thirty — of which $54,000 is what you paid in. Built for anyone deciding whether a small, repeatable amount is worth the trouble, and the 7% is an assumption the model applies, not a return anyone can promise.
Use a negative number if you're spending more or saving less.
What this is worth over time
In 1 year
+$1,859
If you invest $150/month, future-you gains about +$1,859.
In 10 years
+$25,963
If you invest $150/month, future-you gains about +$25,963.
In 30 years
+$182,996
If you invest $150/month, future-you gains about +$182,996.
Make it real
Turn that +$150/month into a plan
A number on a slider is a hypothetical. The same amount, set up once and tracked every month, is a Leap.
Free · 2 minutes · No credit card.
Assumptions
- Investing assumes a 7% real (inflation-adjusted) return — an assumption, not a guarantee.
- Cash uses 0% real — no growth, just deposits.
- Debt uses APR avoided (simplified estimate, not a payoff schedule).
Estimates only. Not financial advice.
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How is this calculated?
Three models, one monthly amount, three horizons. The formulas are written out here so you can see what the projection assumes before you trust the size of it.
Investing: monthly contributions, compounded at an assumed 7%
The investing model is the standard future-value-of-an-annuity formula: each monthly contribution is compounded at one twelfth of 7% for every month left in the horizon, and the results are added up. At $150 a month that comes to about $1,859 after a year, about $25,963 after ten years and about $182,996 after thirty — of which $54,000 is money you paid in and roughly $129,000 is growth. 7% is an assumption this calculator applies, not a rate anyone is offering you, and the arithmetic would be exactly as confident at 4% or at 10%.
The 7% is a long-run real rate, so the output is in today’s dollars
The figure used here is a real — inflation-adjusted — return, the convention most retirement projections follow for a diversified stock portfolio. That means the numbers are meant to be read in today’s purchasing power rather than as the dollar figure that would appear on a statement in thirty years, which inflation would make larger and worth no more. It also means you should not subtract inflation from these results a second time. The rate is fixed at 7% in this version of the tool: the amount, the use of funds and the debt APR are yours to change, the investing rate is not yet.
Cash: the deposits, and nothing else
Money held as cash is shown as the sum of what you put in — $150 a month for ten years is $18,000, full stop. That is deliberately unflattering and it is the honest comparison against a real return: cash keeps its number and loses purchasing power at the rate of inflation, which is the price of being able to reach it tomorrow. It is the right home for an emergency fund and the wrong home for money with a thirty-year job.
Debt: interest avoided, estimated rather than amortised
Paying extra against a balance is modelled as interest you stop paying rather than a return you earn, because that is what it is — and at a 22% APR, interest avoided is a guaranteed 22%, higher than any expected market return, which is why debt usually wins this comparison outright. The estimate is deliberately simple: the extra principal you paid, multiplied by the APR, halved to reflect that the average dollar sits for roughly half the period. It is a sense of scale over one to a few years, not a payoff schedule, and it overstates the long horizons badly — a real balance gets cleared, at which point there is no more interest to avoid. For an actual payoff date, use the credit card calculator linked below.
One, ten and thirty years — and negative numbers too
The three horizons are shown together because the argument for starting early is nearly invisible at one year and overwhelming at thirty: with $150 a month invested at 7%, the third decade adds more than the first two combined. The monthly amount also runs negative, down to -$1,000, which reads the calculation backwards — what a subscription you keep, or a saving you stop, costs the same future.
What will my monthly savings grow to?
Common monthly amounts, invested and compounded at the same assumed 7% the calculator uses. The last column is the part that is growth rather than money you paid in — which is small at ten years and larger than the contributions themselves at thirty.
| Saved each month | After 1 year | After 10 years | After 30 years | Growth in that 30 |
|---|---|---|---|---|
| $25 | $310 | $4,327 | $30,499 | $21,499 |
| $50 | $620 | $8,654 | $60,999 | $42,999 |
| $100 | $1,239 | $17,308 | $121,997 | $85,997 |
| $150 | $1,859 | $25,963 | $182,996 | $128,996 |
| $300 | $3,718 | $51,925 | $365,991 | $257,991 |
| $500 | $6,196 | $86,542 | $609,985 | $429,985 |
Illustrations of one assumption, not projections of your account. They assume the contribution never misses a month and the return arrives smoothly, and no real thirty years works that way.
What this can’t see: that you will not actually contribute the same amount for thirty years, that markets deliver nothing like a smooth 7% — some years are large losses — and that the order the returns arrive in changes the ending balance enormously over a working life. A 7% real return is a planning convention, not a forecast and not a product anyone is selling you; a different assumption gives a different answer, and no assumption makes the outcome certain. Read the output as a sense of scale rather than a balance on a date. Everything here is an estimate for planning. WeLeap is not a registered investment adviser and nothing on this page is personalised financial advice.
Questions people actually ask
How much will saving $150 a month be worth?
Invested consistently at an assumed 7% real return, $150 a month comes to roughly $1,859 after one year, about $25,963 after ten years, and about $182,996 after thirty — of which about $129,000 is growth rather than the $54,000 you paid in. The gap between the ten-year and thirty-year figures is the entire argument for starting early: the last decade contributes more than the first two combined. Held as cash instead, the same $150 a month is $1,800, $18,000 and $54,000 — the deposits and nothing more. These are this calculator's own figures, and they assume the contribution never stops and the return arrives smoothly, which no real market does.
Is saving a small amount each month worth it?
Small amounts do most of their work through time rather than size, so the answer depends far more on how long the money is left alone than on how much it is. At an assumed 7% real return, $25 a month is about $4,327 after ten years and about $30,499 after thirty; $50 a month is about $8,654 and about $60,999. Both end up several times what was paid in. Starting ten years later is what costs: $25 a month for twenty years is about $13,023, so a third less contributed produces well under half the result. The version of this that is genuinely not worth it is a small amount saved while a credit card at 20%-plus is running, because the interest on that balance is larger and guaranteed.
Why do you use 7%?
7% is used here as a long-run real (inflation-adjusted) return for a diversified stock portfolio, which is the convention most retirement projections use. It is a planning assumption, not a prediction and not a product being offered: no single year looks like 7%, and any thirty-year window can land meaningfully above or below it. A projection is only ever as good as its rate, so treat the output as a sense of scale rather than a number to plan a specific date around.
Are these figures adjusted for inflation?
Yes. The 7% used here is a real return, meaning inflation has already been taken out of it, so the results are expressed in today's purchasing power rather than in the larger dollar figure that would show on a statement decades from now. That is why you should not subtract inflation from these numbers a second time — and why a projection built on a nominal rate of 9% or 10% will look bigger while describing the same outcome.
What about market crashes?
This calculator smooths growth into one steady rate, so it does not show the drawdowns a real thirty-year period contains — and every thirty-year period contains several. What it is useful for is direction and magnitude: whether a change is worth thousands or hundreds of thousands. What it cannot tell you is what your balance will be on a particular date, because sequence of returns matters enormously and is unknowable in advance.
Is it better to invest, save cash, or pay off debt?
It depends on the rate attached to each, and only one of the three rates is certain. Paying off a balance at 22% APR avoids 22% guaranteed, which beats an expected 7% from investing precisely because it is not an expectation; cash earning nothing loses value to inflation but is the only one of the three available on the day you need it. That is the usual ordering: a small cash buffer first, then high-interest debt, then investing. This calculator models all three separately — compound growth for investing, deposits only for cash, and interest avoided for debt — so one monthly amount can be compared across them. The debt figure is a rough estimate rather than a payoff schedule, and it overstates long horizons, because a real balance eventually clears and stops charging interest.
Is this financial advice?
No. This is an educational calculator that shows how one monthly change compounds over time using figures you enter yourself. WeLeap is not a registered investment adviser and does not provide personalised investment advice. For guidance specific to your situation, speak to a licensed financial professional.
Estimates to help you think, not financial advice. See all 7 free calculators.
Where the monthly amount comes from
This page assumes you already know the number and are deciding whether it is worth it. These work out what the number should be, and whether it has somewhere more urgent to be first.
- Money PlanThis page starts from a monthly amount you type in. That one derives it: take-home pay for your salary and state, minus essentials, then the order the surplus should go in — match, buffer, debt, retirement, the rest.
- Credit Card PayoffThe debt setting here is a rough estimate of interest avoided, not a payoff schedule. If you have a balance, that one runs the real amortisation: a payoff date, the total interest, and how much sooner an extra monthly payment clears it.
- Emergency Fund TargetThe cash setting shows no growth at all, which is the correct answer for money you might need next month and the wrong one for money you will not. That works out how much of your saving genuinely belongs in reach, so the rest can be invested.
All of them are free and need no account. Browse every WeLeap money calculator.