How much faster does paying $100 extra pay off a credit card?

On $6,000 at 24%, moving from the minimum to a flat $200 cuts the payoff from 252 months to 47 and saves $7,632 of interest. From $300 to $400 it saves 7 months and $534.

Why does the first extra $100 save so much more than the next one?

Because the minimum payment shrinks as the balance shrinks, so it barely dents the debt; a flat payment does not shrink. Once the payment is flat, each further $100 removes less interest because less remains: $1,516 for the second hundred, $534 for the third.

How much interest do you pay on $6,000 at 24% paying only the minimum?

$10,887 over 252 months on the ordinary 1%-plus-interest minimum, so $16,887 paid in total. A flat $300 pays $7,739 over 26 months.

How much faster does an extra $100 a month pay off a credit card?

On $6,000 at 24%, going from the minimum to a flat $200 turns 252 months into 47 and saves $7,632. The next $100 saves $1,516 more. Each extra hundred is worth less than the one before it, and the first one is worth the most by far.

The example

One card, no new spending. The minimum is 1% of the balance plus the month’s interest, floored at $25, so it falls as the balance falls. The flat payments do not fall.

Balance	APR	First minimum payment
$6,000	24%	$180

What it costs

Monthly payment	Months to zero	Total interest	Total paid
The minimum	252	$10,887	$16,887
$200 flat	47	$3,255	$9,255
$300 flat	26	$1,739	$7,739
$400 flat	19	$1,205	$7,205

Read that table twice

Read the first two rows against each other. The minimum starts at $180; $200 is only $20 more in month one. That $20, held flat while the minimum keeps shrinking, is the difference between 252 months and 47, between $10,887 of interest and $3,255. Almost all of it comes from refusing to let the payment fall.

Now read down the flat rows. $200 to $300 saves $1,516 and 21 months. $300 to $400 saves $534 and 7 months. Still real money, but each $100 buys less than the last, because there is less interest left to remove.

So the question in the title has two answers. From the minimum, an extra $100-ish is worth 205 months. From an already-flat $300, an extra $100 is worth 7. Both are true; which one is yours depends on where you are starting.

The honest recommendation

Get off the minimum first, before anything else. It is the cheapest month-one change on the page ($20) and it is worth $7,632. Nothing else here is close.
Then add what you can, knowing the returns fall. $300 beats $200 by $1,516; $400 beats $300 by $534. If the fourth hundred means skipping insurance or the car payment, it is not worth it.
Do not do this out of an empty checking account. A payoff that overdrafts you in the week before payday costs a fee and gets abandoned. The payment that survives the insurance-renewal month is the one that actually finishes.
Do not spread a small extra across several cards. An extra $100 split four ways barely moves any balance. All of it on one card, held flat, is what the table is measuring.

Where these numbers came from

Simulated month by month, not from a formula: interest accrues at APR ÷ 12 on the remaining balance, the payment is applied, the balance updates, until it reaches zero. The minimum row recomputes the minimum every month; the flat rows pay the stated amount every month (or the balance, if less). Rounded to the nearest dollar.

Forgenta runs a payoff plan against your real cards and your real paycheck and shows the date each payment amount buys, side by side. It keeps a floor under your checking account, so the number it suggests is one you can hold flat through the expensive months.

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