How extra payments pay off a loan faster
On any installment loan, each monthly payment is split between interest (the cost of borrowing this month) and principal (what you actually owe). An extra payment goes entirely to principal, so it permanently removes future interest on that amount. The lower balance then means the next payment covers even more principal — a snowball that shortens the loan.
The math behind the payoff date
Each month the loan charges interest of balance × (APR ÷ 12), then your payment plus any extra reduces the balance. Repeating that until the balance hits zero gives the payoff time. This calculator runs the simulation twice — with and without your extra payment — and reports the difference in months and interest.
Which debts to prioritize
- High-interest first. Credit cards and personal loans at double-digit rates cost the most — extra payments here have the biggest payoff.
- Mind prepayment penalties. A few loans charge a fee for paying early; check your terms.
- Keep an emergency fund. Don't drain your savings to prepay; you may need that cash.
- Compare to investing. For very low-rate loans, investing the extra may beat prepaying.
A quick example
A $20,000 balance at 9% with a $400 payment takes about 5 years and 3 months and costs roughly $5,160 in interest. Add $100 a month and it's gone in about 4 years — saving over a year of payments and nearly $1,300 in interest.
Frequently asked questions
How does paying extra each month help?
Every extra dollar goes straight to principal, so it never accrues interest again. That shrinks the balance faster, which means each future payment covers more principal and less interest — compounding the benefit. The result is a shorter loan and lower total interest.
How is the payoff time calculated?
The calculator simulates your loan month by month. Each month it charges interest on the balance (annual rate ÷ 12), subtracts your payment plus any extra, and repeats until the balance reaches zero. The number of months that takes is your payoff time.
What if my payment barely covers the interest?
If your monthly payment is less than or equal to the first month's interest, the balance never goes down and the loan can never be repaid. Increase the payment until it exceeds the monthly interest, and the calculator will show a payoff date.
Are there downsides to paying off a loan early?
A few. Some loans charge prepayment penalties, and money used to prepay a low-rate loan might earn more invested elsewhere. It also reduces your cash cushion. For high-interest debt, though, extra payments are usually one of the best guaranteed returns available.
Disclaimer: Results are estimates for educational purposes only and are not financial advice. Actual loan terms, penalties, and interest handling vary by lender.