$15,000 Debt at 6% Paying $100/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 $100 baseline:

An extra $100 per month here saves $8,948 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 $15,000 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: $15,000 × (6% ÷ 12) = $75 in interest, leaving $25 of your $100 payment to reduce principal. The new balance is $14,975. 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 (0.00500 here), P is the starting balance, and PMT is the monthly payment. For this scenario: 278 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 6% APR, this debt is a lower-priority debt where snowball motivation may matter more than the math. Plug all your debts into our debt snowball calculator to see the optimal sequence.

Frequently asked questions

How long to pay off $15,000 at 6% paying $100 per month?

Short answer: 23y 2m (278 months). You will pay $12,795 in total interest, for a total repayment of $27,795 on the original $15,000. The math: n = -ln(1 - (r × P) / PMT) / ln(1 + r) where r = 0.00500, P = 15000, PMT = 100.

What if I pay an extra $50 per month?

Short answer: Payoff drops to 11y 7m, saving $6,949 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 7y 11m, saving $8,948 in interest. At 6% 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: Not necessarily. At 6% APR, this debt is below the typical equity expected return (~7% real). Paying the minimum and investing the difference is mathematically defensible, especially for tax-advantaged accounts. Always capture employer 401(k) match first regardless. Read our pillar guide: Pay Off Debt or Invest?