How Long to Pay Off $18,000 at 21% APR Paying $600 a Month

If you owe $18,000 on a credit card at 21% APR and pay $600 every month, the balance reaches zero in about 43 months (3 years and 7 months). You will pay roughly $7,747 in interest, for a total of $25,747.

That result assumes the rate stays fixed, no new charges are added, and every payment is made on time. Small changes to any of those assumptions move the date. Interest is roughly $315 in month one, just over half the payment. The payoff takes about three and a half years and costs $7,747 in interest — 43% of the original balance.

Amortization summary for $18,000 at 21% APR with a $600 monthly payment.
Year	Principal paid	Interest paid	Balance at year end
1	$3,769	$3,431	$14,231
2	$4,641	$2,559	$9,589
3	$5,716	$1,484	$3,874
4	$3,874	$273	$0

Amortization summary for $18,000 at 21% APR with a $600 monthly payment.

Year

Principal paid

Interest paid

Balance at year end

$3,769

$3,431

$14,231

$4,641

$2,559

$9,589

$5,716

$1,484

$3,874

$273

What the payment covers in the first year

The first monthly interest charge is about $315. Your $600 payment therefore applies roughly $285 to principal in month one. That ratio improves slowly: by the end of the first year the balance is still close to its starting point, which is why early payoff progress can feel invisible.

Across the full payoff, interest equals about 43% of the original balance. That figure — not the monthly payment — is the real cost of the schedule.

What would shorten the payoff

Raising the payment to $800 cuts the payoff to about 30 months and saves over $3,000. A partial balance transfer can also lower the blended rate without moving the whole balance.

Is consolidation or refinancing worth it?

A 13% five-year consolidation loan on $18,000 costs about $6,100 in interest, roughly $1,600 less than the card. A shorter three-year loan saves more but raises the payment.

Compare the total interest figures, not the monthly payments. A longer loan almost always has a lower payment and a higher total cost.

What to watch

At this balance, utilization is likely high across multiple cards. Improving the reported ratio before applying for a consolidation loan can improve the rate you are offered.

Treat the schedule as a baseline. Re-run the numbers after any rate change, windfall, or change in income.

Frequently asked questions

How long does it take to pay off $18,000 at 21% APR paying $600 a month?

About 43 months, or 3 years and 7 months, assuming a fixed rate and no new charges. Total interest is approximately $7,747.

How much of my first payment is interest?

Roughly $315 of the first $600 payment is interest at 21% APR. The rest reduces principal.

What happens if I pay extra each month?

Extra payments go to principal, which removes future interest. Even a modest increase compounds: the earlier in the schedule the extra arrives, the larger the effect.

Does this include fees?

No. Late fees, annual fees, origination fees, and balance-transfer fees are excluded. Add any fee to the balance if you want to see its effect.