Same $4,100 as the earlier examples, no new charges, paying $200 a month. At 18.9% APR that takes 25 months and $890 of interest, $4,990 total.
The standard advice is to keep a small emergency fund first, then attack the debt — usually $1,000. The logic is that without a buffer, the next surprise goes straight back on the card. The arithmetic points the other way: the card charges 18.9% while a savings account pays about 4%. Both can be true at once, so here is what each choice actually costs.
What $1,000 against the balance does
Put the $1,000 on the card today, balance $3,100, same $200 a month:
- Card at 18.9%, $200 a month: 18 months, $482 interest — saves $408 and 7 months.
- At $130 a month instead: 31 months, $818 interest — saves $794 and 13 months, down from 44 months and $1,612.
The smaller the payment, the more the lump sum is worth — the same pattern as the rate-cut and hardship pieces: at $130 a month, $1,000 of principal today is worth $794 of interest you never pay.
What the savings account pays you instead
Keep the $1,000 in a savings account at 4% APY while you pay the card off:
- Over the 25-month payoff at $200 a month, the $1,000 earns about $85.
- Over the 44-month payoff at $130 a month, it earns about $155.
Compare: paying the card saves $408 of interest at $200 a month and forgoes about $85 of yield — you come out roughly $320 ahead. At $130 a month the net is roughly $640 ahead ($794 saved minus about $155 forgone). The 14.9-point gap between 18.9% and 4% is doing the work; no savings account closes it.
Smaller lumps scale the same way: $500 against the balance at $200 a month saves $223 and 3 months; $2,000 saves $676 and 13 months.
The case for keeping some cash anyway
The arithmetic assumes the $1,000 is spare. If it is your only buffer, the calculation changes — not because the interest math changes, but because the next surprise has nowhere else to go:
- A $600 car repair with no cash goes on the card at 18.9%, and you are paying interest on the repair while you are still paying off the balance.
- Keeping $500 and putting $500 on the card still saves $223 and 3 months at $200 a month — most of the gain, with a buffer intact.
The fund is insurance, not an investment. Insurance costs money; here the premium is the interest you keep paying on the $500 you held back. That is a fair price for not having to borrow at 18.9% when something breaks. What is not a fair price is holding the full $1,000 in savings while a $4,100 balance compounds at 18.9% — that is paying 18.9% to earn 4%.
The rebuild rule
The compromise that keeps both sides honest: keep one month of the smallest realistic emergency — $500 here — put the rest on the card, and then rebuild the fund with the payment itself. At $200 a month, the card is gone in 18 months instead of 25; the $200 a month that was going to the card then becomes the fund, and it reaches $1,000 in 5 months. You end up debt-free 7 months sooner and the fund is back, with about $320 more in your pocket than if you had kept the whole $1,000 sitting in savings.
This is not financial advice — it is arithmetic on one balance, one rate, and one payment, with the assumptions stated: the savings rate is assumed at 4% APY, no new charges, and the emergency is assumed to be the kind a $500 buffer covers. Change any of them and the numbers move; the method does not.
Try the baseline on the free calculator: https://alapha888.github.io/irregular-income-debt-baseline/
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