Emergency fund
Work out how many months of essential spending your savings actually cover, the balance you need for a real safety net, and how long a fixed monthly deposit takes to get there. Cover is measured against essential spending, not income, because that is what the fund has to replace.
| Line | Amount | Basis |
|---|---|---|
| Essential monthly spend | $3,200 | Housing, food, utilities, transport, insurance |
| Target fund | $19,200 | 6 × $3,200 |
| Already saved | $4,000 | 20.8% of the target |
| Gap remaining | $15,200 | Still to fund |
| Monthly contribution | $600.00 | 18.8% of essential spend |
| Months to target | 24 | 2.00 years at 4.00% APY |
| Interest earned on the way | $881.77 | Compounding on the running balance |
| Cover today | 1.25 months | $4,000 ÷ $3,200 |
Emergency funds belong in cash-equivalents: a high-yield savings account, money market fund or short treasury. The point is access, not return.
spend × months · months of essential cover
max(0, target − saved) · the amount still to fund
B(1 + i) + deposit · i = (1+APY)^(1/12) − 1; deposit at month end
saved / spend · runway in months today
A clear path from inputs to results.
An emergency fund is measured in months of essential spending, not in months of income, because it only has to replace what you cannot switch off. This calculator converts your essential monthly spend into a target balance, measures how much of that target you already hold, and walks the balance forward month by month to show how long a fixed deposit takes to close the gap.
How to use
- Enter your essential monthly spend — housing, food, utilities, transport and insurance.
- Add what you have already set aside for emergencies.
- Choose how many months of cover you are targeting; three to six is the usual range.
- Set the monthly deposit you can sustain without dipping into it.
- Enter the APY on the account the money actually sits in.
- Read the months-to-target figure and the deposit ladder below it.
The formula
Reference: Standard sinking-fund recursion with monthly compounding; target follows the conventional months-of-essential-spend rule used by CFPB and FDIC consumer guidance.
Worked example
$2,850 essential spend, $6,500 saved, 6 months of cover, $450/month at 4.5% APY
- Essential monthly spend $2,850.
- Already saved $6,500.
- Target 6 months of cover.
- Deposit $450 a month into an account paying 4.5% APY.
- 1
Target: 2,850 × 6 = $17,100. Gap: 17,100 − 6,500 = $10,600.
- 2
Monthly rate: 4.5% / 12 = 0.375%.
- 3
After 21 months the balance is about $16,846 — still short.
- 4
After 22 months it reaches $17,358, which clears the target.
- 5
The deposit overshoots because the final month lands a full $450 on top of an almost-funded balance.
Target $17,100 · gap $10,600 · 22 months (1.83 years) at $450/month · balance at goal $17,358.
Interpreting the result
Twenty-two months feels long because the gap is 3.7 months of essential spending. The deposit ladder shows the leverage: at $800 a month the same gap closes in 13 months, at $1,600 in 6. The target does not move — only the time does — which is why raising the deposit rate is usually easier than trimming the target.
Assumptions & limitations
- Cover is measured against essential spending only. Discretionary spending can be cut in a crisis, so counting it inflates the target.
- The deposit is made at the end of each month, which is the conservative convention; depositing at the start shortens the plan by about one month.
- The APY is constant and the account is a cash-equivalent. An emergency fund should not be invested in anything that can fall when you need it.
- The fund is not raided during the projection. A withdrawal resets the clock, which is why the balance path is the honest view.
- Tax on interest is ignored; for most balances it is small, and it is not the reason to hold the fund.
Frequently asked questions
How many months of cover do I actually need?
Three months is the floor for a stable salaried job with a second income in the household. Six is the common recommendation for a single income. Nine to twelve is prudent for freelancers, commission-paid roles, or anyone whose sector hires in cycles.
Where should the money sit?
A high-yield savings account, money market fund, or short treasury ladder. You are buying access and stability, not yield. Keep it at a separate institution if that stops you from spending it.
Why does the calculator say the final balance overshoots the target?
Because deposits are a fixed dollar amount. The month that crosses the target adds a full deposit, so the balance lands above it. The excess is not wasted — it becomes the first month of the next tier of cover.
Should I count my 401(k) or brokerage account?
No. The point of the fund is that it is available without a penalty and without selling at a bad price. Retirement accounts and equities fail both tests, so they belong in a different plan.
Should I build the emergency fund before paying off debt?
Build a starter fund of one month first, then decide. High-interest credit card debt usually costs more than the fund earns, but going to zero savings to clear it leaves you borrowing again at the first setback.
Methodology last reviewed 2026-10-18. Results are informational and not financial or engineering advice — see our disclaimer.