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How to work out the date your debt is paid off

The arithmetic, why the number is usually worse than people expect, and the two things that move it most.

Prices and features checked 22 August 2026. Both change — check before you buy.

Why a balance is not an answer

"I owe $6,000" tells you almost nothing. At $150 a month on a 19.99% card that is five and a half years and about $3,900 in interest — you will pay for it roughly twice. At $250 a month it is two years and three months and about $1,200. Same debt, wildly different life.

The number that actually helps is a date. Dates can be planned around; balances just sit there.

The arithmetic

Month by month: your balance earns interest at the annual rate divided by twelve, that interest is added, then your payment comes off. Repeat until the balance reaches zero.

So on $6,000 at 19.99%, the first month's interest is 6000 × (0.1999 ÷ 12), about $100. Pay $150 and only $50 actually comes off the debt. That is the part people are not told, and it is why progress feels so slow at the start.

The trap worth knowing about

If your payment is smaller than the monthly interest, the balance grows no matter how long you keep paying. At 19.99% on $6,000 that threshold is about $100 a month. Pay $95 forever and you will owe more at the end than you did at the start.

It is worth checking where that line sits for each of your debts. Anything close to it needs attention before anything else does.

The two things that move the date

• Paying more. On that $6,000 card, an extra $50 a month clears it about two years sooner and saves roughly $1,500 in interest — because every extra dollar comes off principal, so the interest shrinks every month afterwards too.
• Paying the expensive one first. If you have several debts, the same spare money kills more interest aimed at the highest rate. Aiming at the smallest balance instead clears one sooner, which some people need to keep going — that one is about motivation, not maths, and both answers are legitimate.

Doing it for real

The sums above are one debt at a time. Real life is several debts, different rates, different due dates, minimum payments that change with the balance, and a paycheck that has to cover rent first.

That is what WhenZero does: it walks forward day by day for three years across all of them at once, accrues interest daily rather than monthly, applies minimums, and sends whatever is spare at the debt you choose. The output is a date, and it moves when you change something.