Interest on a $20,000 line of credit at 8.45% is $140.83 a month. Pay $600 a month and the line is gone in 3.3 years, with $2,874.69 of interest along the way.
What does the calculator tell you?
Type in the balance, your rate and what you pay each month. You get the interest for the first month, the time until the balance hits zero and the total interest over that whole stretch. It all assumes that you don’t borrow another cent.
The number to look at first is the interest-only payment. That’s the least you can pay before the balance starts to shrink at all. On the default line it’s $140.83, so a payment of $140 never clears the debt.
How fast does a bigger payment pay it off?
The balance stays at $20,000 and the rate at 8.45% in this table. Only the monthly payment changes.
| Monthly payment | Time to pay off | Total interest |
|---|---|---|
| $200 | 14.5 years | $14,714.74 |
| $300 | 7.6 years | $7,098.63 |
| $400 | 5.2 years | $4,739.74 |
| $600 | 3.3 years | $2,874.69 |
| $800 | 2.3 years | $2,076.84 |
| $1,000 | 1.8 years | $1,632.93 |
What does $600 a month look like in practice?
You owe $20,000 and pay $600. The first month charges $140.83 in interest, so $459.17 of your payment actually reduces the debt. After 39 payments the line is cleared, and you’ve handed over $22,874.69 in all.
Push the payment to $1,000 and it’s finished in 22 payments. Interest drops to $1,632.93, which is $1,241.76 less than the $600 plan.
Now go the other way. A payment of $141 barely beats the interest, and the calculator shows about 961 payments and $115,444.70 in interest. Near the interest-only amount, a few dollars either way changes the outcome enormously.
Should you pick the smallest payment you can afford?
Not if you can help it.
Choose the payoff date you want, try a few amounts until the time to pay off matches, then set up a fixed transfer for that sum. A payment you set once is easier to keep than whatever is left at the end of the month.
There’s a trade-off, of course. A $400 payment clears the default balance in 5.2 years, while $800 does it in 2.3 years and cuts interest from $4,739.74 to $2,076.84. If money is tight, take the lower figure and look at it again every few months, with your rate in mind.
Where does a payment in between land?
Say Dana in Halifax can stretch from $500 to $700 a month on the same $20,000 at 8.45%. At $500 the line takes 48 payments, four full years, and costs $3,573.12 in interest. At $700 it takes 33 payments and costs $2,408.92. That extra $200 a month saves $1,164.20 and gets her out of debt 15 months sooner.
What could throw the numbers off?
Most lines of credit float with the lender’s prime rate. The real cost moves when prime does, but the calculator holds your rate fixed for the whole payoff, so type in a higher one to see what a rise would do. A full point is a good test: at 9.45% the $600 plan still takes 39 payments but the interest grows to $3,290.75, about $416 more.
Minimum payments are often set close to the interest, which keeps the debt alive for years. Some lenders also charge an annual fee, and that isn’t included here. Every new withdrawal adds to the balance and restarts the clock, so run it again after you borrow more.
Where do you start with your own line?
Grab your latest statement and read off the balance and the rate, then enter both. If the payoff date is further out than you’d like, find a few extra bucks a month and test again. Some lenders only ask for the interest each month, which feels easy but leaves the balance exactly where it was, so use the interest-only figure as a floor, never a plan.
How we checked the figures
Monthly interest is the balance times the yearly rate, divided by 12. Each payment goes to interest first and the balance second, and the last payment is trimmed to fit. The rate hint on the calculator says prime plus your lender’s margin, but your credit agreement has the exact figures. This site has no connection with any lender or government.
A line secured against your home works differently, and the HELOC calculator estimates how much you could borrow on it. If you’d rather have a fixed repayment plan, compare it with the personal loan calculator. Card debt at a higher rate goes in the credit card payoff calculator.
About this calculator
- What it does
- See the interest and payoff time on a line of credit.
- Category
- Loans and Debt
- Last checked
- September 30, 2026
- Result type
- Estimate for information only, not tax advice.
Frequently asked questions
How is line of credit interest worked out?
Take the balance, multiply by the yearly rate and divide by 12. On $20,000 at 8.45% that's $140.83 for the month.
What if my payment is too low?
If it doesn't cover the monthly interest, the balance never falls. The calculator shows a warning when that happens.
How much does a bigger payment save?
On the default line, paying $1,000 a month instead of $600 saves you $1,241.76 in interest.
Will the rate change?
Probably. Most lines float with prime, so the real cost can move, while the calculator keeps your rate fixed.
Are new withdrawals included?
No. It assumes you borrow nothing more, so run it again after any new withdrawal.
Sources and updates
Updated: . How we check rates · Editorial team · Updates