Is an Extra $100 a Month Worth It? The Math on Early Loan Payoff

It's one of the most common money questions there is: I have a little extra each month — should I throw it at the loan? The answer is almost always yes, but the *size* of the yes surprises people.

Why extra dollars punch above their weight

A regular payment does two jobs: it covers the month's interest first, then reduces the balance with whatever's left. An extra payment skips the line — 100% of it hits principal directly. And because interest is calculated on the balance, shrinking the balance shrinks *every future month's* interest charge. The savings compound in reverse.

Concretely: on an $18,000 loan at 9% with a $375 payment, adding $100 a month typically saves over a thousand dollars in interest and cuts more than a year off the payoff. The higher the rate and the longer the remaining term, the more dramatic the effect.

The two traps to check first

• **Payment application.** Some lenders apply extras to "next month's payment" instead of principal — which saves you nothing. Mark extra payments "apply to principal" and confirm on the following statement.
• **The order of operations.** If you carry multiple debts, extra dollars belong on the highest-rate one first. An extra $100 against a 24% card beats the same $100 against a 6% car loan, every time.

A loan payment doesn't exceed its monthly interest? Then the balance never falls — that debt isn't being repaid, it's being rented. Check yours.

When extra payoff is the wrong move

Honesty requires the other side: if your loan is cheap (say, a 3% mortgage) and you have no emergency fund or unmatched 401(k) money on the table, the extra $100 may earn more elsewhere. The comparison is simple — the loan's rate is a guaranteed return; weigh it against what the alternative realistically pays and how much you value the peace of a smaller balance.

Run your exact loan below — balance, rate, payment, and the extra you're considering. The calculator shows both timelines side by side: months saved, interest saved, and your new debt-free date. Module 3 of the Wealth System turns this into a complete demolition plan across every debt you carry.