$20,000 Debt at 15% Paying $1,000/Month: How Long to Pay Off?

The numbers

What if you paid more each month?

Even small increases in monthly payments produce outsized savings because the extra dollars go entirely toward principal — they bypass the interest charge completely. Two acceleration scenarios on top of the $1,000 baseline:

An extra $100 per month here saves $327 in interest — substantially more than the extra $100 itself across the payoff period. This is the highest-leverage move available to anyone carrying high-rate debt: every accelerated dollar earns the equivalent of the APR in saved interest.

Year-by-year amortization

Here is exactly how the $20,000 balance shrinks year by year, with interest and principal portions broken out:

The math

Each month, interest accrues at the daily-equivalent rate (we use APR ÷ 12 for simplicity, which is how most credit cards and personal loans work). For the first month: $20,000 × (15% ÷ 12) = $250 in interest, leaving $750 of your $1,000 payment to reduce principal. The new balance is $19,250. The next month earns slightly less interest because the balance is smaller, so slightly more goes to principal — and the cycle accelerates as the debt shrinks.

The closed-form formula for months-to-payoff: n = -ln(1 - (r × P) / PMT) / ln(1 + r), where r is the monthly rate (0.01250 here), P is the starting balance, and PMT is the monthly payment. For this scenario: 24 months.

Snowball vs avalanche relevance

If this is one of several debts, the order in which you attack them matters. The snowball method attacks smallest balance first for psychological wins; the avalanche method attacks highest APR first to minimize total interest. At 15% APR, this debt is a moderate-priority avalanche target. Plug all your debts into our debt snowball calculator to see the optimal sequence.

Frequently asked questions

How long to pay off $20,000 at 15% paying $1,000 per month?

Short answer: 2 years (24 months). You will pay $3,159 in total interest, for a total repayment of $23,159 on the original $20,000. The math: n = -ln(1 - (r × P) / PMT) / ln(1 + r) where r = 0.01250, P = 20000, PMT = 1000.

What if I pay an extra $50 per month?

Short answer: Payoff drops to 1y 10m, saving $173 in interest. Every extra dollar goes entirely to principal, which is why even small increases produce large total savings — you avoid all the interest that principal would have generated for the rest of the loan.

What if I pay an extra $100 per month?

Short answer: Payoff drops to 1y 9m, saving $327 in interest. At 15% APR, every $100 of accelerated payment earns the equivalent of the APR in interest saved — a guaranteed return that beats almost any plausible investment.

Should I pay this off before investing?

Short answer: Probably yes. At 15% APR, eliminating this debt is mathematically equivalent to earning a guaranteed 15% return — better than most stock-market scenarios. Most fee-only planners recommend paying off any debt above 8% APR before investing in a taxable brokerage account, while still capturing employer 401(k) match. Read our pillar guide: Pay Off Debt or Invest?