How much should I keep before attacking the debt?

Try one month of essential expenses in the target field and compare it against three. A small buffer removes most of the exposure that actually matters, the ordinary small shocks, for a fraction of what a full fund costs. The full three to six months is better built once the high-rate debt is gone.

Why does holding cash cost so much against a credit card?

Because the two rates are not comparable as quoted. Savings interest is taxable, so a 4.2% APY in a 22% bracket is 3.3% to you; avoided card interest is untaxed and runs at 20%. The gap is close to seventeen points a year on every dollar you hold rather than repay. Savings versus debt paydown works that comparison out in isolation.

Can I just use a credit card as my emergency fund?

No, and this is the assumption the whole exercise is built to counter. Available credit means borrowing at the rate you were escaping, at the exact moment your income has stopped and your ability to repay is weakest. It converts a cash-flow problem into a compounding one.

What counts as an essential expense?

What you would still have to pay if your income stopped: rent or mortgage, food, utilities, insurance, transport and minimum debt payments. Not restaurants, subscriptions or holidays, in the situation the fund is for, those stop. Sizing the target on total spending rather than essentials overstates it substantially.

What about my 401(k) match while I do this?

Take it, before either path. An employer match is a 50% or 100% guaranteed return on the day you contribute, which beats both the debt rate and the cushion by a wide margin. The match against paying off debt works that out; this calculator assumes it is already handled.

Which debt should I attack once the cushion is set?

The highest rate first costs the least interest, though clearing a small balance first can help you keep going. Snowball versus avalanche puts a figure on that trade across all your balances at once.

Should I Build an Emergency Fund or Pay Off Debt?

Should I build an emergency fund or pay off debt first? Paying the debt always ends with more money: cash earns a few percent after tax and the debt charges far more. The real question is what the cushion costs, and how many months without one it saves you, which is what this prices.

Example numbers

The verdictfrom an example

The cushion costs $2,240 and removes 11 months of having no buffer, about $204 for each month of cover.

Worked on $12,000 at 19.9%, $3,200 of expenses, $500 a month spare. Change anything below to use yours.

The cushion costs: $2,240
Exposure it removes: 11 months
Price of that protection: $204 a month

The figures behind it

The cushion costs: $2,240; In net worth by the horizon, against attacking the debt first.
Exposure it removes: 11 months; Months you would otherwise spend with no buffer at all.
Price of that protection: $204 a month; The cost divided by the months of exposure removed. This is the number to judge.
Cushion target: $9,600; 3 months of $3,200 in essential expenses.
Cushion first: funded by: Month 17; Debt free in 2 years, 7 months, paying $4,250 of interest.
Debt first: funded by: Month 28; Debt free in 1 year, 5 months, paying $1,866 of interest.

Cash in hand on both paths

Years from today

Build the cushion firstClear the debt first

Payment scheduleShow

The table scrolls sideways

Month	A · cash	A · debt	A · cover	B · cash	B · debt	B · cover
1	$1,503	$11,882	Exposed	$1,003	$11,382	Exposed
2	$2,007	$11,762	Exposed	$1,005	$10,753	Exposed
3	$2,512	$11,639	Exposed	$1,008	$10,114	Exposed
4	$3,019	$11,515	Exposed	$1,011	$9,465	Exposed
5	$3,527	$11,389	Exposed	$1,014	$8,804	Exposed
6	$4,037	$11,260	Exposed	$1,016	$8,133	Exposed
7	$4,548	$11,130	Exposed	$1,019	$7,451	Exposed
8	$5,060	$10,997	Exposed	$1,022	$6,757	Exposed
9	$5,574	$10,862	Exposed	$1,025	$6,052	Exposed
10	$6,090	$10,725	Exposed	$1,028	$5,335	Exposed
11	$6,606	$10,586	Exposed	$1,030	$4,606	Exposed
12	$7,124	$10,444	Exposed	$1,033	$3,865	Exposed
13	$7,644	$10,300	Exposed	$1,036	$3,112	Exposed
14	$8,164	$10,154	Exposed	$1,039	$2,347	Exposed
15	$8,687	$10,005	Exposed	$1,042	$1,568	Exposed
16	$9,210	$9,853	Exposed	$1,045	$777	Exposed
17	$9,600	$9,564	Covered	$1,075	$0	Exposed
18	$9,626	$8,905	Covered	$1,895	$0	Exposed
19	$9,652	$8,236	Covered	$2,717	$0	Exposed
20	$9,679	$7,555	Covered	$3,542	$0	Exposed
21	$9,705	$6,863	Covered	$4,369	$0	Exposed
22	$9,732	$6,159	Covered	$5,198	$0	Exposed
23	$9,758	$5,444	Covered	$6,030	$0	Exposed
24	$9,785	$4,717	Covered	$6,863	$0	Exposed
25	$9,812	$3,978	Covered	$7,699	$0	Exposed
26	$9,838	$3,227	Covered	$8,538	$0	Exposed
27	$9,865	$2,463	Covered	$9,378	$0	Exposed
28	$9,892	$1,687	Covered	$10,221	$0	Covered
29	$9,919	$898	Covered	$11,066	$0	Covered
30	$9,946	$95	Covered	$11,914	$0	Covered
31	$10,694	$0	Covered	$12,764	$0	Covered
32	$11,540	$0	Covered	$13,616	$0	Covered
33	$12,389	$0	Covered	$14,470	$0	Covered
34	$13,240	$0	Covered	$15,327	$0	Covered
35	$14,094	$0	Covered	$16,186	$0	Covered
36	$14,949	$0	Covered	$17,047	$0	Covered
37	$15,808	$0	Covered	$17,911	$0	Covered
38	$16,668	$0	Covered	$18,777	$0	Covered
39	$17,531	$0	Covered	$19,646	$0	Covered
40	$18,396	$0	Covered	$20,517	$0	Covered
41	$19,263	$0	Covered	$21,390	$0	Covered
42	$20,133	$0	Covered	$22,266	$0	Covered
43	$21,005	$0	Covered	$23,144	$0	Covered
44	$21,880	$0	Covered	$24,024	$0	Covered
45	$22,757	$0	Covered	$24,907	$0	Covered
46	$23,636	$0	Covered	$25,792	$0	Covered
47	$24,518	$0	Covered	$26,680	$0	Covered
48	$25,402	$0	Covered	$27,570	$0	Covered
49	$26,289	$0	Covered	$28,463	$0	Covered
50	$27,178	$0	Covered	$29,358	$0	Covered
51	$28,069	$0	Covered	$30,255	$0	Covered
52	$28,963	$0	Covered	$31,155	$0	Covered
53	$29,860	$0	Covered	$32,057	$0	Covered
54	$30,758	$0	Covered	$32,962	$0	Covered
55	$31,660	$0	Covered	$33,869	$0	Covered
56	$32,563	$0	Covered	$34,779	$0	Covered
57	$33,470	$0	Covered	$35,691	$0	Covered
58	$34,378	$0	Covered	$36,606	$0	Covered
59	$35,289	$0	Covered	$37,523	$0	Covered
60	$36,203	$0	Covered	$38,443	$0	Covered

What this result assumes

Both paths pay the same $817.26 every month, the minimum plus your spare cash, and are measured on the same date. Only the order changes.
The minimum payment is always made first on both paths. Nobody defaults on a debt to build savings, and a model that allowed it would not describe a real choice.
Savings interest is taxed as ordinary income at your marginal rate, so the cushion earns considerably less than its quoted APY. That is why holding cash against a card is expensive.
The exposure count is months in which your cash is below the target, not a probability of needing it. This model cannot tell you how likely a shock is, only what covering it costs.
A card with available credit is not an emergency fund. Borrowing at the rate you are trying to escape, at the moment your income has just stopped, is the situation the cushion exists to prevent.

Methodology

Reviewed September 1, 2026

The arithmetic answer, and why it is not the answer

On expected value this is not a close question. A savings account yields a few percent, and after income tax rather less; a credit card charges twenty. Every dollar parked in cash instead of thrown at the balance costs you the difference, so attacking the debt first always ends with more money. The calculator confirms it every time.

That answer is also close to useless on its own, because it prices only one side. The cost of having no cushion is not the interest you forgo. It is that the next unexpected bill — a car repair, a deductible, a month without work — goes straight back onto the card at the rate you were trying to escape. That is not a hypothetical failure mode; it is the ordinary way people stay in revolving debt for years.

So the useful output is not which path wins but what the cushion costs and what it buys: the dollars given up, the months of exposure removed, and the price per month of cover. Those are figures you can actually judge against your own job security and how likely a shock feels.

How the two paths are run

Both spend exactly the same amount every month — the debt’s minimum payment plus your spare cash — and both are measured on the same date, so neither can win by quietly spending more.

The minimum is always paid first on both paths. Nobody defaults on a debt in order to save, and a model that allowed it would not describe a choice anyone faces. What differs is where the spare goes: on one path into the cushion until it reaches target and then at the debt, on the other at the debt until it clears and then into savings.

Interest is charged monthly on the debt at its rate, and credited monthly on savings at the quoted APY reduced by your marginal tax rate — savings interest is ordinary income, which is a large part of why holding cash against a card is expensive.

Sizing the cushion, and the middle path

The target is months of essential expenses: rent, food, utilities, insurance and minimum debt payments. Not discretionary spending, because in the situation the fund exists for, the discretionary spending stops. Three months is a common floor; six is more appropriate for variable income, a single earner, or a role that is slow to replace.

The choice is not really binary, and the calculator can show you why. Set the target to one month rather than three: a small buffer removes most of the exposure that matters — the small shocks that would otherwise hit the card — for a fraction of what a full fund costs. Many people are best served by a starter cushion, then the debt, then the rest of the fund.

One thing to be plain about: available credit on a card is not an emergency fund. Borrowing at 20% at the exact moment your income has stopped is the outcome the cushion is there to prevent, not a substitute for it.

Assumptions

Both paths spend the same amount each month and are measured on the same date.
The debt’s minimum payment is always made in full, on both paths.
Savings interest is taxed annually as ordinary income at your marginal rate.
The debt rate and savings APY are constant throughout, though card rates are variable.
No emergency actually occurs during the period — exposure is counted, not simulated.
Essential expenses are constant and do not rise with inflation.
No new borrowing or spending is added to the debt.
The behavioural value of holding a cushion is real but not priced.
Any employer retirement match is assumed already taken, since it beats both paths.

Sources

Common questions

Should I build an emergency fund or pay off debt first?: Build a small cushion first, then attack the debt, then finish the fund. Paying the debt always wins on pure arithmetic, cash earns a few percent after tax against a card charging twenty, but running with no buffer at all means the next unexpected bill goes back on the card, which is how people stay in debt for years. The calculator prices that trade rather than pretending it does not exist.
How much should I keep before attacking the debt?: Try one month of essential expenses in the target field and compare it against three. A small buffer removes most of the exposure that actually matters, the ordinary small shocks, for a fraction of what a full fund costs. The full three to six months is better built once the high-rate debt is gone.
Why does holding cash cost so much against a credit card?: Because the two rates are not comparable as quoted. Savings interest is taxable, so a 4.2% APY in a 22% bracket is 3.3% to you; avoided card interest is untaxed and runs at 20%. The gap is close to seventeen points a year on every dollar you hold rather than repay. Savings versus debt paydown works that comparison out in isolation.
Can I just use a credit card as my emergency fund?: No, and this is the assumption the whole exercise is built to counter. Available credit means borrowing at the rate you were escaping, at the exact moment your income has stopped and your ability to repay is weakest. It converts a cash-flow problem into a compounding one.
What counts as an essential expense?: What you would still have to pay if your income stopped: rent or mortgage, food, utilities, insurance, transport and minimum debt payments. Not restaurants, subscriptions or holidays, in the situation the fund is for, those stop. Sizing the target on total spending rather than essentials overstates it substantially.
What about my 401(k) match while I do this?: Take it, before either path. An employer match is a 50% or 100% guaranteed return on the day you contribute, which beats both the debt rate and the cushion by a wide margin. The match against paying off debt works that out; this calculator assumes it is already handled.
Which debt should I attack once the cushion is set?: The highest rate first costs the least interest, though clearing a small balance first can help you keep going. Snowball versus avalanche puts a figure on that trade across all your balances at once.

All debt →