How Long Will My Savings Last? Calculator
β Finance & MoneyWondering how far your savings would stretch if your income changed or stopped? Put in what you've saved, what you spend and any money still coming in. See how many months you could cover β and what might buy you more time.
Your savings runway
Where your monthly expenses come from
Watch your savings runway
The line follows the exact monthly simulation. Switch the window or view to look closer β the underlying calculation does not change.
The shaded area is your spendable balance after each month's bills, income and assumed return. The zero line is the point at which the runway ends.
See the month-by-month numbers
| Period | Opening | Expenses | Income | From savings | Return | Closing |
|---|
What would buy you more time?
These are hypothetical changes on the same savings, income, return and inflation assumptions. Nothing above is overwritten.
Make your money last longer
What monthly spending would let this money last a full months?
These are planning estimates, not predictions. They assume the income, spending and rates you enter follow the stated pattern. Real interest, investment returns, prices and unexpected costs can change the result. Tax and account fees are not modelled unless specifically provided.
A savings balance is a number. Your runway is a plan.
A big savings balance can feel reassuring. But the number in your account doesn't tell you how long you could live on it. That depends on what leaves each month, what keeps coming in, and how quickly those two things change.
$24,000 sounds like a healthy cushion. Spend $3,000 a month with no income and it covers eight months. Keep earning $1,000 a month, and the same savings last twelve. The money hasn't changed. The gap it needs to fill has.
That's what this calculator is for. It turns a bank balance into a stretch of time you can actually picture β whether you're taking a break between jobs, testing a move, or asking what would happen if your paycheque stopped for a while.
And the most interesting result isn't always the date the money runs out. Sometimes it's seeing how much longer it could last with a smaller bill, a little income on the side, or a savings buffer you choose not to touch.
Try the numbers you actually spend rather than your best-case budget. A realistic runway is more useful than an impressive one.
The surprising maths of making money last
Your balance might stay the same for a while, but the time it buys can change dramatically. Here's the surprising part.
A side gig can be worth four extra months
An extra $500 a month can turn 12 months into 16. Start with $24,000 in savings, $3,000 in monthly spending and $1,000 of income. Your savings fill a $2,000 gap for 12 months. Earn another $500 and the gap falls to $1,500 β giving the same savings 16 full months. Same bank balance. A third more breathing room.
Ten dollars a day can buy two extra months
A $10-a-day change could buy you more than two extra months. Treat a month as 30 days for this example: spending $300 less per month takes the same $2,000 savings gap down to $1,700. A $24,000 cushion then lasts about 14.1 months instead of 12. No magic investment returns β just a smaller hole to fill.
A giant savings balance can have a tiny runway
$100,000 isn't a ten-year cushion if you're spending $10,000 a month. With no other income and no interest, six figures in savings cover ten months at $10,000 a month, but one hundred months at $1,000 a month. The number on the account statement doesn't tell you the whole story; the burn rate does.
Your reserve can buy peace of mind, but not extra spending
Keeping $4,000 off-limits changes a one-year runway into ten months. Start with $24,000 and a $2,000 monthly shortfall. All $24,000 could cover 12 months. Protect $4,000 so you don't touch it, and the spendable $20,000 covers 10 months. You're not poorer β you're choosing to keep a cushion.
A paycheque can be a bigger asset than a bigger balance
Earning $1,000 a month can be worth the same runway as adding $12,000. With $24,000 and $3,000 monthly expenses, zero income gives eight months. With $1,000 income, it gives twelve. To get twelve months with no income instead, you'd need $36,000 in savings β another $12,000. Under these simple assumptions, ongoing income has enormous runway value.
These are arithmetic illustrations with round US-dollar assumptions, not predictions for any household.
How does the savings runway calculator work?
It starts with a simple question: how much of your monthly spending must come out of savings? For a quick answer with no interest and no rising bills, that monthly shortfall divides into your available balance. For a longer, more realistic estimate, the calculator repeats that process month by month, adding any assumed return and adjusting expenses or income only when you ask it to.
This is sometimes called a savings depletion calculator: the same runway, seen as a balance falling toward zero.
The quick formula
Monthly shortfall = max(0, monthly expenses β monthly other income)
Spendable savings = savings balance β protected reserve
Runway in months = spendable savings Γ· monthly shortfall
Worked example: ($24,000 β $0) Γ· ($3,000 β $1,000) = 12 months. This is the easy-to-understand baseline, not the full engine once returns, annual increases or monthly surpluses are enabled.
The monthly simulation
The real result comes from a deterministic month-by-month cash-flow simulation. Cash flows happen at the start of each month; the assumed effective annual return then accrues on whatever remains.
Monthly return = (1 + annual return)^(1/12) β 1 Expenses in month t = starting expenses Γ (1 + annual expense increase)^yearIndex Income in month t = starting income Γ (1 + annual income increase)^yearIndex yearIndex = floor((t β 1) Γ· 12) Net gap = expenses β income Opening balance β net gap = balance before return Closing balance = balance before return Γ (1 + monthly return)
Expenses and income therefore step up at months 13, 25, 37 and so on β not at month 12. Months 1β12 use the starting amounts. A positive net gap is paid from savings. A negative net gap is a surplus added to savings.
Full months, partial months and the horizon
If the opening spendable balance cannot cover a complete month's net gap, the calculator records the full months already funded and estimates the final fraction as opening balance Γ· that month's net gap. That fraction is a pro-rata approximation of the remaining shortfall, not an exact bill date.
The projection runs for up to 1,200 months (100 years). If the spendable balance is still above zero at the end, the result says No shortfall within the 100-year projection rather than inventing a depletion date or claiming the money lasts forever. If income already covers expenses and no later gap appears, it says No savings draw required under these assumptions.
Interest and rising expenses β a worked fixture
With $30,000 savings, $3,000 monthly expenses, $1,000 monthly income, a 3% effective annual return and 2.5% annual expense growth, the model funds 15 complete months plus about 0.147 of month 16, or about 15.15 months. Returns during the 15 complete months total approximately $529.30. Expenses in months 13β15 are $3,075 and income remains $1,000. The partial month is pro-rated and earns no full month of return.
The default example is simpler: $24,000 spendable, a $2,000 monthly gap and no return or inflation. Month 1 closes at $22,000, month 6 at $12,000 and month 12 at $0.
The βmake it last N monthsβ solver
The goal solver keeps savings, reserve, income, return and both growth rates fixed. It repeatedly simulates exactly the target number of months with a candidate starting expense, checking that every one of those months is fully fundable. A bounded binary search finds the largest starting expense that succeeds. Ending at exactly $0 after the target month counts as success.
With $24,000, no return or inflation and $1,000 other income, a 24-month target gives a maximum starting expense of $2,000/month β $1,000 less than the current $3,000. This is a planning ceiling under the entered assumptions, not a guaranteed safe withdrawal rate.
Assumptions, limitations and why this isn't a retirement guarantee
- Rates are assumptions, not offers or predictions. Investment values and account interest can change, including losses.
- Spending is an estimate. Unexpected medical, housing, repair and other bills are not automatically included.
- The model runs in regular monthly blocks. Actual bills and income occur on varying dates.
- Inflation changes the spending assumption only if enabled. It doesn't secretly alter currency conversion or taxes.
- Taxes, investment fees, account withdrawal restrictions, benefits eligibility and country-specific retirement rules are not modelled. If you enter net other income, the calculator treats it as available money and does not calculate its tax.
- This is not probability modelling. A smooth 5% assumption differs from market returns that jump up and down, so sequence-of-returns risk can matter when drawing down investments.
- A protected reserve is excluded from the available runway. It remains your money and is shown separately.
- No US or Australian rule is universally applied. Financial situations differ around the world; enter your own currency and assumptions.
Background methodology and sources
These links are background reading, not endorsements of CozyCalcs.
- U.S. SEC Investor.gov β Compound Interest Calculator. Demonstrates withdrawals as negative contributions, compounding and rate assumptions.
- Morningstar β How Retirees Can Determine a Safe Withdrawal Rate. Real withdrawals adjusted for inflation, and the distinction between assumptions and guarantees.
- Morningstar β How to Avoid Outliving Your Retirement Savings? It's All in the Sequence. Explains sequence-of-returns risk for variable market outcomes.
- ASIC Moneysmart β Savings Goals Calculator. A supplementary example of stating interest, timing, inflation and tax assumptions. Australian reference only, not a default for this global calculator.
Frequently asked questions
How long will $10,000 in savings last?
It depends on your monthly shortfall. With $1,000 a month coming out of savings, $10,000 covers ten months. With a $2,000 monthly shortfall, it covers five months. If the shortfall falls to $1,000, it covers ten months. Enter your own expenses and income to get a result that means something for your situation.
How do I calculate how many months my savings will last?
Start with the savings you can actually spend. Subtract any money you plan to leave untouched, then work out how much of your monthly expenses isn't covered by income. Divide the spendable savings by that monthly gap for a quick estimate. This calculator also lets you model hypothetical interest and expenses rising over time.
Should I enter all my expenses or only essential bills?
Use the spending level you realistically expect to maintain. If you would cut back while living on savings, enter that leaner budget β but include irregular bills by averaging them across the year. Running a second scenario with your normal spending is a useful reality check.
Should I include part-time work, benefits, freelance income or a pension?
Yes, if you reasonably expect the money to be available to spend, include it as monthly other income. Use the net amount after any relevant withholding, and consider a separate scenario without uncertain income. The calculator does not check eligibility or calculate tax for any country.
Does this calculator include interest on my savings?
Only if you enter an annual return above or below zero in the advanced settings. The starting value is 0%, so the basic answer is easy to follow. Any return you enter is hypothetical and constant; real savings-account interest rates and investment outcomes can change.
What happens if my costs rise with inflation?
Add an annual expense increase in advanced settings. The calculator keeps expenses at their starting level for the first twelve months, then increases them at the beginning of each following year. Other income stays flat unless you separately choose to grow it. Higher expenses can shorten your runway, even if the starting month's budget looks manageable.
What if my income is greater than my expenses?
Under the simple flat-income and flat-spending scenario, you would not need to draw from savings, and any monthly surplus could increase the balance. If spending rises faster than income, a shortfall might still appear later. That's why the calculator evaluates every month instead of assuming the first month's result lasts forever.
Can I keep an emergency buffer untouched?
Yes. Enter a protected reserve in advanced settings. For example, if you have $24,000 but want to protect $4,000, the calculator uses only $20,000 to fund your expenses. It doesn't spend the remaining $4,000 or treat it as extra interest-bearing cash in the model.
Is this the same as the 4% retirement withdrawal rule?
No. The 4% rule is a historical retirement-withdrawal guideline associated with particular investment portfolios and assumptions, not a promise. This tool projects your cash flow using the savings, spending, income and hypothetical rates you choose. It does not simulate thousands of market paths, pensions or the chance of running out of money.
Does changing USD to another currency convert my savings?
No. Currency selection changes how amounts are labelled and displayed, not their numerical values. Enter amounts in the currency you actually use. The underlying arithmetic works the same for dollars, euros, pounds, rupees and other supported currencies, but the calculator doesn't provide live exchange rates.
Why does my result show part of a month?
The final fraction is a pro-rata estimate of the remaining shortfall in the month the spendable balance stops covering a complete gap. It is not an exact calendar date or a bill-by-bill schedule.
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