Calculator overview
Inputs and outputs
This summary comes from the calculator's published input and output contract.
Inputs
- Savings APY (required)
-
Unit fraction Default 0.04 Range 0 to 0.06
About this input
The annual percentage yield the account pays, as the bank quotes it, before any tax. It is read as an effective annual rate, so twelve months at the monthly rate compound to exactly this figure; dividing a nominal rate by twelve instead gives a slightly shorter time at the same number. The FDIC put the national average savings rate at 0.37 percent in September 2026, while the top of Bankrate's list of high-yield accounts paid 4.20 percent.
- Months Of Cover (required)
-
Unit months Default 6 Range 1 to 24
About this input
How many months the fund should carry the gap between essential spending and any income that would continue, if your pay stopped. Published guidance runs from three to six months for most households to eight or twelve for a single earner or an irregular income. The verdict compares the months you choose with the median and the average spell of unemployment in the Bureau of Labor Statistics figures this calculator carries. A whole number of months, at least one.
- Tax Rate On Interest
-
When omitted Blank
Unit fraction Default Not set Range 0 to 0.5
About this input
Optional. The combined rate of income tax you pay on savings interest, federal and state together. Leave it blank if the interest is untaxed or the tax is paid from other money, and it reads as nothing. The APY is reduced by this share before it compounds, so a 4 percent APY taxed at 25 percent grows the fund at 3 percent a year.
- Surprise Bill Reserve
-
When omitted Blank
Unit $ Default Not set Range 0 to 15000
About this input
Optional. A separate reserve for an unexpected bill such as a car repair or a medical expense, kept apart from the months of cover. Leave it blank and it reads as the share of a month of essential spending that Vanguard's rule sets for spending shocks; enter 0 to size the fund on months alone. In the Federal Reserve's 2025 survey 59 percent of adults had a major unexpected expense in the year, against 7 percent who were laid off.
- Emergency Savings
-
When omitted Blank
Unit $ Default Not set Range 0 to 30000
About this input
Optional. Money already set aside for emergencies, in an account you could draw on at once. Leave it blank if you are starting from nothing, and it reads as nothing. It counts toward the target and earns interest from the first month, so what is still to save, the share already saved and every month count start from it.
- Continuing Monthly Income
-
When omitted Blank
Unit $/month Default Not set Range 0 to 28000
About this input
Optional. Income that would keep coming in if your own pay stopped: a partner's pay, a pension, or the unemployment benefit you expect. Leave it blank and it reads as none, so the months of cover pay for all the essential spending, which is what published guidance assumes. Entered, only the gap it leaves is covered, and income at or above the essential spending leaves the fund sized for surprise bills alone.
- Monthly Contribution (required)
-
Unit $/month Default 250 Range 0 to 3000
About this input
What you can put into the fund at the end of each month. Every month count here is worked out at this figure, and the table shows what each step up or down from it is worth. Zero is accepted, and then only the interest on what is already saved builds the fund.
- Essential Monthly Expenses (required)
-
Unit $/month Default 4000 Range 500 to 28000
About this input
What the household has to pay in a month to keep going: housing, utilities, food at home, insurance, transportation, health care, minimum debt payments and childcare, with anything you could stop paying for left out. The fund is sized on this rather than on everything you spend, as Fidelity sizes it. Households in the middle fifth of incomes spent about 3,937 a month on housing, food at home, transportation and health care alone in 2024. The needs total from the 50/30/20 Budget Split calculator can be entered here: a total below 500 enters as 500, one above 28,000 as 28,000, and it rounds to the nearest 5.
Outputs
- Table1 Months Column Axis
-
No unit declared
About this output
The values across the top of the table: the months of cover, in equal steps either side of yours and never below the table's floor. Read a column to hold the months fixed and vary the contribution. The middle entry is your own figure; for a short cover the lowest entries repeat at that floor, which is the table running out of room rather than an error.
- Table1 Months Column Input
-
Unit months
About this output
Machinery, and NOT an input. The same for the column axis: Excel substitutes into it while filling the table, and the rest of the time it mirrors the months of cover.
- Surprise Bill Layer
-
Unit $
About this output
The layer of the target kept for surprise bills: the reserve you entered, or, when that is left blank, the share of a month of essential spending that Vanguard's rule sets for spending shocks. It is not spent on a job loss in this calculation, because a surprise bill is far more likely than a layoff and the two are separate goals.
- Months To Target
-
Unit months
About this output
How many months of contributions, with interest, it takes before the savings first reach the whole target, a balance within half a cent counting as there. Zero means the savings already meet it. A count equal to the horizon the model looks ahead means the target is not reached within that horizon at this contribution, and the status line says so. This is the figure the table tabulates.
- Still To Save
-
Unit $
About this output
How far the savings already set aside are from the target, never below nothing.
- Table1 Months Values
-
Unit months
About this output
The body of the table: the months until the savings first reach the whole target, worked out again for every combination of the two axes. A value equal to the horizon the model looks ahead means the target is not reached within it at that pair. In an answered state zero means the savings already meet the target at that pair; when the inputs are refused, a pair whose own values are refused also reads zero. One hundred and twenty-one values, each the whole calculation run again; it is a component of the table rather than a result on its own.
- Target In Months Of Spending
-
Unit months
About this output
The target divided by the essential spending, so it can be set beside the three to six months most guidance quotes. It is more than the months of cover by the reserve, and less when other income would continue.
- Table1 Months Row Input
-
Unit currency/month
About this output
Machinery, and NOT an input. Excel substitutes each value from the row axis into this mirror while it fills the table; the rest of the time it mirrors the monthly contribution. Change the contribution, never this: the axis is derived from it, so editing the mirror moves the axis while the table walks and the table comes out meaningless.
- Table1 Months Corner
-
Unit months
About this output
Machinery. Excel requires the figure being tabulated to sit in the table's top-left corner, where it means nothing to a reader, so it is formatted away. It holds the months until the whole target is saved.
- Table1 Months Row Axis
-
No unit declared
About this output
The values down the left of the table: the monthly contribution, in equal steps either side of yours and never below the table's floor, so for a small contribution the top entries repeat at that floor. Read a row to hold the contribution fixed and vary the months of cover. The middle entry is your own contribution.
- Months To Reserve
-
Unit months
About this output
How many months of contributions, with interest, it takes before the savings cover the reserve for surprise bills, a balance within half a cent counting as there. Zero means it is already covered. A count equal to the horizon the model looks ahead means the reserve is not reached within that horizon.
- Cover Verdict
-
No unit declared
About this output
How the months of cover compare with the median and the average spell of unemployment in the Bureau of Labor Statistics figures this calculator carries, each turned from weeks into months. The reserve for surprise bills is left out of the comparison. The measure counts spells still running when the survey was taken, not finished ones, so it is a guide to how long people go without work rather than a forecast of your own.
- Emergency Fund Target
-
Unit $
About this output
The fund to aim for: the reserve for surprise bills plus the months of cover. It is in today's dollars and makes no allowance for inflation, which leaves the same fund covering less each year it is not topped up.
- Contributions To Target
-
Unit $
About this output
What you will have paid in by the month the target is reached: the monthly contribution times the months. Blank when the target is not reached within the horizon the model looks ahead.
- After Tax APY
-
Unit fraction
About this output
The APY less the tax on its interest: the rate the fund grows at in this calculation. It equals the APY when no tax rate is entered.
- Contribution For Two Years
-
Unit $/month
About this output
The level amount a month that would reach the target in two years at the same rate, allowing for what is already saved. It is nothing when the savings reach the target on interest alone within that time.
- Model Status
-
No unit declared
About this output
Reads OK, or explains why the inputs are not valid or why the answer deserves a second look.
- Monthly Draw
-
Unit $/month
About this output
The part of essential spending the fund would have to pay each month if your pay stopped: the spending less any income that would continue, never below nothing. With no continuing income entered it is the whole essential spending.
- Interest To Target
-
Unit $
About this output
The interest the account will have paid by the month the target is reached, after any tax on it. At a low rate it is a small part of the target, which is the plainest measure of what the account's rate is worth. Blank when the target is not reached within the horizon the model looks ahead.
- Funded Share
-
Unit fraction
About this output
The savings already set aside as a share of the target, never above 100 percent.
- Income Loss Layer
-
Unit $
About this output
The layer of the target that covers a loss of income: the monthly gap multiplied by the months of cover. At that gap it lasts exactly the months you chose, which is why the months, and not the whole target, are what the verdict on unemployment compares.
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Methodology
Purpose and model boundary
Sizes an emergency fund in two layers, a reserve for the surprise bill that far more households meet than a layoff, plus months of only the part of essential spending that other income would not cover, then works out how long a savings account's APY takes to build it and whether the months of cover outlast a typical spell of unemployment. Use it to set a target you can reach and to see what the monthly amount and the rate change about when you get there.
The workbook is the calculation authority. The page groups and explains its inputs and returned figures; it does not reproduce the financial logic in browser code.
Inputs and units
| Input | Unit | Accepted range | What it means |
|---|---|---|---|
| Savings APY | % | 0% through 6% | The annual percentage yield the account pays, as the bank quotes it, before any tax. |
| Months Of Cover | months | 1 through 24 | How many months the fund should carry the gap between essential spending and any income that would continue, if your pay stopped. |
| Tax Rate On Interest | % | 0% through 50% | Optional. |
| Surprise Bill Reserve | $ | 0 through 15000 | Optional. |
| Emergency Savings | $ | 0 through 30000 | Optional. |
| Continuing Monthly Income | $/month | 0 through 28000 | Optional. |
| Monthly Contribution | $/month | 0 through 3000 | What you can put into the fund at the end of each month. |
| Essential Monthly Expenses | $/month | 500 through 28000 | What the household has to pay in a month to keep going: housing, utilities, food at home, insurance, transportation, health care, minimum debt payments and childcare, with anything you could stop paying for left out. |
Governing relationships
Monthly gap = max(essential monthly expenses - continuing monthly income, 0).
Emergency fund target = surprise-bill reserve + months of cover × monthly gap.
The current balance and end-of-month contributions grow at the after-tax monthly rate derived from the entered annual percentage yield.
Months to target is the first month whose projected balance reaches the target, within the model's ten-year horizon.
Calculation sequence
Monthly gap = max(essential monthly expenses - continuing monthly income, 0).Emergency fund target = surprise-bill reserve + months of cover × monthly gap.The current balance and end-of-month contributions grow at the after-tax monthly rate derived from the entered annual percentage yield.
Months to target is the first month whose projected balance reaches the target, within the model's ten-year horizon.
Rerun the calculation across the delivered two-way table and chart ranges so the effect of changing the stated assumptions is visible.
Outputs and interpretation
| Output | Role | Unit | What it means |
|---|---|---|---|
| Months To Target | primary | months | How many months of contributions, with interest, it takes before the savings first reach the whole target, a balance within half a cent counting as there. |
| Still To Save | primary | $ | How far the savings already set aside are from the target, never below nothing. |
| Emergency Fund Target | primary | $ | The fund to aim for: the reserve for surprise bills plus the months of cover. |
Model Status reports whether the workbook accepted the current entries and whether an assumption deserves review. It describes model health, not whether the calculated outcome is good or bad.
Every figure above is returned by the workbook. The page arranges and formats the figures; it computes none of them.
Validation and status logic
| Condition | Returned status |
|---|---|
| The entries are accepted and no additional model warning applies | OK |
| at this contribution the target is not reached within the horizon the model looks ahead; raise the monthly contribution. | CHECK: at this contribution the target is not reached within the horizon the model looks ahead; raise the monthly contribution. |
| the savings already meet the target, so nothing more needs to be set aside. | CHECK: the savings already meet the target, so nothing more needs to be set aside. |
| the income that would continue covers the essential spending, so the fund is sized for surprise bills only. | CHECK: the income that would continue covers the essential spending, so the fund is sized for surprise bills only. |
Assumptions and limitations
- Essential spending, continuing income and the monthly contribution are held level.
- Inflation is not applied, so a fund held for years will cover less in real terms.
- The time-to-target chart stops after ten years even when the target lies beyond it.
Restrictions and non-computing states
Numeric entries outside the accepted ranges above are refused before calculation. A state the workbook itself marks NOT VALID returns no usable answer. Optional blanks follow the workbook's documented treatment and are not silently replaced by page logic.
The sensitivity table is a set of recalculations across its two axes. It is not a probability surface or a forecast.
Errors and warnings
NOT VALID means the entered question cannot be computed as stated. CHECK means the workbook returned figures but identified an assumption or combination that deserves attention. OK means the current entries passed the workbook's model checks; it does not mean the financial outcome is recommended.
A transport or service failure is reported separately and never replaced with a stale or partial result.
References
Sources and further reading
These sources provide background; they do not supply the calculator's assumptions or certify its result. Values that vary by household, offer, place or time remain inputs for the reader to check.
This calculator is informational and is not financial, investment, or tax advice. Verify important decisions against current official rules, the actual offer or account terms, and an appropriately qualified professional.
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