Enter what you owe, the interest rate and your current monthly payment, then add an extra amount each month, a one-time payment, or both. The calculator shows the new payoff date, how many months sooner you are debt-free and exactly how much interest you save — for car loans, student loans, personal loans and mortgages.
Paid off in
3 yrs 7 mo
April 2030
Interest saved
$728
1 yr sooner
Total interest
$2,388
vs $3,116 on schedule
Plan
Monthly
Months
Payoff
Interest
Current schedule
$395.00
55
April 2031
$3,116
With extra payments
$495.00
43
April 2030
$2,388
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How the payoff is calculated
The balance is simulated month by month: interest for the month is balance × (APR ÷ 12), the payment plus any extra is subtracted, and the loop repeats until the balance reaches zero. The month count gives the payoff date; adding up the monthly interest gives the total cost. The same simulation without the extra payments is the baseline used for the savings figure.
interest this month = balance × APR ÷ 12
new balance = balance + interest − (payment + extra)
Worked example: $18,500 at 6.9 % APR with a $395 payment takes 55 months and costs about $3,100 in interest. Adding $100 a month clears it in 43 months and saves about $730; a $2,000 lump sum today on top of that brings it to 38 months and total interest of roughly $1,900.
What $50, $100 and $200 extra does
Loan
On schedule
+$50/mo
+$100/mo
+$200/mo
$18,500 car loan, 6.9 %, $395/mo
55 mo, $3.1k interest
48 mo, saves ~$410
43 mo, saves ~$730
35 mo, saves ~$1.2k
$35,000 student loan, 5.5 %, $380/mo
10 yrs, $10.6k
8.6 yrs, saves ~$1.7k
7.4 yrs, saves ~$2.9k
5.9 yrs, saves ~$4.5k
$300,000 mortgage, 6.5 %, $1,896/mo
30 yrs, $383k
27.8 yrs, saves ~$34k
26 yrs, saves ~$61k
23.1 yrs, saves ~$104k
Rounded illustrations from the same month-by-month method; run your own numbers above.
Frequently asked questions
Every extra dollar goes straight to principal, so next month’s interest is charged on a smaller balance. The saving compounds: $100 extra a month on an $18,500 car loan at 6.9 % with a $395 payment cuts 12 months off the 55-month term and saves about $730 in interest.
A lump sum paid today saves slightly more than the same total spread over months, because the principal drops sooner. In practice do both: put a windfall (tax refund, bonus) toward the balance and set up a fixed extra amount each month.
Yes — any fixed-rate loan with monthly compounding: auto loans, personal loans, most federal and private student loans, and mortgages. For a mortgage use the principal-and-interest part of your payment, not the escrow for taxes and insurance.
Compare the loan’s APR with what you can safely earn. Paying off a 24 % credit card is a guaranteed 24 % return; a 3 % mortgage is usually worth keeping while you invest. In between (6–9 % car and personal loans) most people do both, and always keep an emergency fund first.
Most US auto and student loans have none, and federal student loans never do. Some personal loans and older mortgages carry a penalty in the first 2–3 years — check the promissory note. When you send extra money, tell the lender to apply it to principal, not to future payments.