Paying off a simple interest loan early
Because interest is charged only on what you still owe, every extra dollar of principal you pay stops earning interest for the lender immediately.
Updated October 30, 2026. Examples are calculated with the formulas shown on our formula page.
A worked example
A $15,000 loan at 9% for four years has a payment of $373.28 and costs $2,917.23 in interest. Paying $150 extra each month pays it off in 33 months instead of 48 and cuts interest to $1,952.35, a saving of $964.88.
See what extra payments save
Monthly payment: $495.03
- Total interest: $4,701.80
- Total paid: $29,701.80
- Paid off in: 60 months
- Interest per day at the start: $4.79
Estimates for a fixed-rate loan with equal monthly payments. Lenders that use daily simple interest charge interest on the exact days between payments, so paying early or late changes the interest slightly.
Before you pay extra
- Check the contract for a prepayment penalty.
- Tell the lender to apply extra money to principal.
- Ask for a payoff quote if paying in full: it includes interest accrued since the last payment.
- Keep the account in good standing until the lender confirms it is paid in full.
Frequently asked questions
Is there a penalty for paying off a simple interest loan early?
Most personal and auto loans have no prepayment penalty, but some do. Look for a “prepayment” clause in your contract or ask the lender before making a large payment.
Should extra payments go to principal?
Yes. Ask your lender to apply extra money to principal rather than to future payments. Some lenders otherwise treat it as paying the next installment early, which saves less.
Is it better to pay off a loan early or invest?
Paying off a loan earns a guaranteed return equal to its interest rate. If the rate is high, paying it down usually wins. Keep an emergency fund first, and consider your own situation.