One $5,000 card at 24% APR, $125 minimum held fixed, no new charges. Numbers from this site's public payoff engine. The delayed-start figures use the same monthly loop with the extra switched on at month 13 and month 25.
The first $25 is worth twice the second
Extra payments do not scale evenly. Each one erases interest that would have been charged, and the interest left to erase gets smaller as the balance falls — so the same $25 buys less the later it arrives. On this card the first $25 buys 26 months and $1,837.40. The second $25 buys 13 months and $834.05. Counted in money, the second step is worth 45% of the first: $834.05 ÷ $1,837.40 = 45.4%. Counted in months it is 50%: 13 ÷ 26. Both are correct; they are just two different denominators. The money ratio is the smaller one because the months the first step buys are the expensive ones — they sit early, where the balance is large and every month skipped would have been charged interest at the full rate.
| Extra per month | Months to clear | Total interest | This step bought |
|---|---|---|---|
| $0 (minimums) | 82 | $5,159.49 | — |
| +$25 | 56 | $3,322.09 | 26 mo · $1,837.40 |
| +$50 | 43 | $2,488.04 | 13 mo · $834.05 |
| +$75 | 36 | $2,000.56 | 7 mo · $487.48 |
| +$100 | 30 | $1,678.99 | 6 mo · $321.57 |
| +$150 | 23 | $1,277.13 | 3 mo · $185.68 |
| +$200 | 19 | $1,035.87 | 2 mo · $107.47 |
The steps are counted in whole months, so they do not fall in a straight line in the last column — going from +$25 to +$50 bought 13 months, and going from +$50 to +$75 bought 7. Measured per $25 of extra payment, the +$50-to-$75 step is worth 7 months and the $0-to-$25 step 26, so the first step still buys about 3.7 times as much per dollar as that one. The shape is what matters: most of the available saving sits in the first $25, and nearly all of it sits below $100.
The same $50, started later
When you start is a separate lever from how much you send, and it is the one people leave on the table because the payment feels like a decision rather than a date. Keep the amount fixed at $50 and move only the start month.
| Start | +$25: months / interest | +$50: months / interest | Cost of waiting (+$50) |
|---|---|---|---|
| Month 1 (now) | 56 · $3,322.09 | 43 · $2,488.04 | — |
| Month 13 | 62 · $3,868.53 | 51 · $3,231.36 | 8 mo · $743.32 |
| Month 25 | 67 · $4,309.92 | 58 · $3,856.28 | 15 mo · $1,368.24 |
Waiting a year to start the same $50 costs $743.32 and 8 months. Waiting two years costs $1,368.24 and 15 months. Nothing about the payment changed — only the month it began.
Where the cost of waiting comes from
The twelve waiting months are not free. They are charged $1,164.71 of interest, the same as any other twelve months on the minimum, and they leave the balance at $4,664.70. When the $50 finally starts, it is pushing against a balance that has already been through a year of interest, and it has 12 fewer months to compound. That is the whole mechanism: the extra dollar is worth most when the balance is biggest, and the balance is biggest at the start.
It also explains why the delayed run is not simply 12 months longer. Starting at month 13 finishes at month 51 instead of 43 — 8 months later, not 12 — because the extra still gets a long runway against a balance that is still large. The month-by-month split on this same card shows how slowly the principal moves while you wait.
What this page is not saying
It is not an argument for a particular method, and it is not a reason to feel bad about a month you could not pay extra. Two things are true at once: on one card there is no order to choose, so the amount and the start date are the only levers; across several cards the order is worth real money but less than the amount — $30,074.90 across twelve portfolios against $2,671.45 from a single $50 on a single $5,000 card.
If $50 is a stretch, $25 does most of the work: 26 of the 39 months. What each extra level buys on a four-card portfolio runs the same question at a larger size, and the rate decides how much each extra dollar is worth in the first place.
Reproduce these numbers
The constant-extra figures come straight from /api/payoff. Post {"debts": [{"name": "Card", "balance": 5000, "apr": 24, "minPayment": 125}], "extra": 50} and it returns 43 months and $2,488.04; change extra to 25 and it returns 56 months and $3,322.09. The delayed-start runs are the same monthly loop with the extra switched on at a later month, which the public endpoint does not expose — the loop is interest = balance × 24 ÷ 1200, then pay = min(125, balance + interest) + 50 once the start month is reached. Note the + interest inside the minimum: the cap is on a payment that has to cover that month's interest, not just the balance you opened the month with. Written as min(125, balance) alone, a final month that opens at $30 and is charged $0.60 would pay $30 and leave the $0.60 behind, and you would run one more month than this page. Run the loop until the balance is at or below a cent and round only at the end — rounding the interest to cents each month drifts about a cent over a year. APR goes in as a percentage, and the minimum is held fixed, the same conventions as every page here.
Frequently asked
Does an extra $50 a month actually help?
Yes, and by more than the amount suggests. On a $5,000 card at 24% with a $125 minimum, the extra $50 takes the payoff from 82 months to 43 and the interest from $5,159.49 to $2,488.04 — $2,671.45 and 39 months saved.
Is $50 better than $25, or is it just more?
The first $25 is worth more than the second. On the same card, $25 takes the payoff to 56 months and $3,322.09 of interest — 26 months and $1,837.40 saved. The next $25 takes it to 43 months and $2,488.04, another 13 months and $834.05. Measured in money, the second $25 buys 45% of what the first one bought: $834.05 against $1,837.40. Measured in months it is 50%: 13 against 26. The two ratios differ because the last 13 months of a payoff have little interest left to save, so each month saved is worth fewer dollars than a month saved early.
What if I start the $50 next year instead of now?
The same $50 starting in month 13 finishes in 51 months and costs $3,231.36, which is 8 months and $743.32 worse than starting now. Starting in month 25 finishes in 58 months and $3,856.28 — 15 months and $1,368.24 worse.
Why does waiting a year cost so much?
Because the twelve waiting months are charged $1,164.71 of interest and leave the balance at $4,664.70. The extra payment then starts against a balance that is 12 months older, and the months it would have spent compounding are gone. Same dollars, fewer months of work.
Should I pay the extra or pay the smallest card first?
Both, in this order: send the extra at all, then decide where it goes. On one card there is no order to choose. Across several cards the order is worth hundreds — $30,074.90 across twelve portfolios — while the amount is worth thousands on a single $5,000 balance.
Does the same $50 do more on a higher-rate card?
Yes. The extra dollar erases interest that would otherwise have been charged, so the more expensive the rate, the more each dollar erases. The same $50 on a 24% card is worth more than on a 12% card, and the gap widens the longer the balance stays open.