Loan Calculator with Extra Payments
See when your loan will be paid off if you pay extra, and how much interest you save. Add an extra every month, once a year or as a one-off lump sum, starting from the original loan or from today's balance and payment. You get the new payoff date, the months saved, the interest saved and both amortization schedules.
Calculate Your Savings with Extra Payments
How to use this calculator
- Choose where to start. The original loan (amount, rate and term, with an optional current balance), or just your current balance, rate and monthly payment.
- Add your extra payments. Any mix of a monthly extra, a yearly extra in the month you choose, and a one-off lump sum in a given month.
- Press Calculate Savings. The first line gives the new payoff month, how much sooner it is and the interest saved; below it are both amortization schedules, month by month.
Monthly, yearly or one-off: what each saves
A $20,000 loan at 6% over 5 years, starting January 2026, has a payment of $386.66 and costs $3,199.36 in interest over 60 payments. The same loan with each kind of extra payment:
| Extra payment | Payments | Total interest | Interest saved |
|---|---|---|---|
| None | 60 | $3,199.36 | $0.00 |
| $100 every month | 47 | $2,444.38 | $754.98 |
| $1,200 every December | 48 | $2,589.40 | $609.96 |
| $1,200 once, in the first month | 56 | $2,801.47 | $397.90 |
$100 a month and $1,200 each December put the same amount toward the loan each year, but the monthly extra saves more because each dollar reaches the balance sooner and stops being charged interest earlier. The longer and larger the loan, the bigger the effect: a $300,000 mortgage at 6.5% over 30 years ($1,896.20 a month) with $200 extra a month is paid off in 277 payments instead of 360, 6 years 11 months sooner, saving $103,448.79 in interest.
How extra payments shorten a loan
Each month the lender charges interest on the balance you still owe: balance × annual rate ÷ 12. Your regular payment covers that interest first and the rest reduces the balance. An extra payment goes entirely to the balance, so next month's interest is charged on less, more of the regular payment goes to principal, and the loan ends early. The regular payment itself does not change.
The regular payment for a loan of P over n months at a monthly rate r is P × r(1+r)n ÷ ((1+r)n − 1). The calculator uses that for the original loan, or your own payment if you start from your current balance, then runs the schedule month by month with and without your extras.
Car loans, personal loans and simple interest
Car loans usually charge simple interest; the Consumer Financial Protection Bureau says it is generally more common than precomputed interest, and describes it as interest “based on your actual outstanding balance on the day your payment is due”, which is why paying extra reduces what you owe (CFPB, simple vs precomputed interest). That is the model this calculator uses, one month's interest on the remaining balance each month. A lender that counts interest by the day will differ slightly depending on when each payment arrives. On a precomputed interest loan, the CFPB notes, extra payments do not reduce the interest owed, so this calculator does not apply. The same test works for a personal loan: if your agreement charges interest on the outstanding balance, this calculator fits it.
Before you pay extra
Make sure it reaches the balance. Some lenders credit extra money against a future payment, which the CFPB calls “paid ahead status” and says is most common with federal student loans; it moves your due date rather than cutting the balance. Ask the lender or servicer to apply it to principal, and check your next statement (CFPB, additional student loan payments).
Check for a prepayment penalty. The CFPB describes it as a fee some mortgage lenders charge for paying off all or part of a mortgage early, and says it typically applies only if you pay off the whole balance within a set number of years, usually three or five (CFPB, prepayment penalties). Your loan documents will say.
Paying every two weeks instead of monthly means 26 half-payments a year, which add up to 13 monthly payments rather than 12; the Biweekly Mortgage Calculator models it directly.
Frequently Asked Questions (FAQ)
FAQ Index
- Can I include extra payments in a loan calculator?
- When will my loan be paid off if I pay extra?
- How much interest do extra payments save?
- Is a lump sum or an extra monthly payment better?
- Does this work for a simple interest loan, like a car or personal loan?
- Will extra payments lower my monthly payment?
- How do I make sure my extra payment goes to principal?
- Are there penalties for paying extra?
- Can I use it for several debts at once?
- What if my loan has a variable interest rate?
Yes. This calculator takes three kinds at once: a fixed extra every month, an extra once a year in a month you choose, and a one-off lump sum in a given month. It shows the payoff date, the number of payments and the interest with and without them, side by side, with both amortization schedules.
Enter your loan and the extra you plan to pay; the first line of the result gives the new payoff month and how much sooner that is. If you do not know the original loan terms, choose “My current balance and monthly payment” and it projects forward from this month.
It depends on the rate, the balance and how long is left. A $20,000 loan at 6% over 5 years costs $3,199.36 in interest; paying $100 extra a month clears it 13 months sooner and saves $754.98. A $300,000 mortgage at 6.5% over 30 years with $200 extra a month is paid off 6 years 11 months sooner and saves $103,448.79. Both figures are from this calculator.
For the same money each year, paying it monthly saves a little more, because each dollar reaches the balance sooner. On the $20,000, 6%, 5-year loan, $100 a month saves $754.98 while $1,200 each December saves $609.96. A single $1,200 lump sum in the first month saves $397.90.
Yes. On a simple interest loan the interest is worked out on the balance you actually owe, so paying extra shrinks the balance and the interest with it; this calculator charges a month's interest on the remaining balance each month. A lender that counts interest by the day will differ slightly, depending on when each payment arrives. It does not apply to precomputed interest loans, where the CFPB notes that extra payments do not reduce the interest owed.
No. The required payment stays the same and the loan simply ends sooner. The payment only goes down if you refinance or your lender agrees to recast the loan, which is a separate arrangement.
Tell the lender or servicer to apply it to the principal balance, and check the next statement. The CFPB warns that some lenders instead credit extra money against a future payment, called “paid ahead status” and most common with federal student loans, which does not reduce your balance; you can ask them to put it toward the balance instead.
Some mortgages have a prepayment penalty, a fee for paying off all or part of the mortgage early, and other loans can have similar terms. The CFPB says mortgage penalties typically apply only if you pay off the whole balance within a set number of years, usually three or five. Your loan documents say whether yours has one.
It models one loan at a time. For several debts with different rates, the Debt Payoff Calculator compares paying them off in different orders.
The calculator holds the rate you enter for the whole loan. For a variable rate, use today's rate for an estimate and recalculate when the rate changes; the real payoff date and interest will differ.
Method & sources
This calculator is educational, not advice. It estimates payoff dates and interest from the numbers you enter; it is not a payoff quote, a loan offer or financial advice. Confirm figures and how extra payments are applied with your lender before relying on them.
- Formula
Monthly rate r = annual rate / 100 / 12.
Original-loan mode: regular payment M = P x r(1+r)^n / ((1+r)^n - 1), where P is the original loan amount and n the term in months; if r = 0, M = P / n. Current-balance mode: M is the monthly payment you enter.
Each month: interest = balance x r (on the balance before that month's payment); the payment made is M plus any extra due that month (the monthly extra from its start month, the yearly extra in its chosen month, the one-off in its month), capped at balance + interest in the final month; balance falls by payment - interest.
The schedule is run twice, without extras and with them, from the same start. Interest saved = total interest without extras - total interest with extras. Months sooner = difference in the number of payments.
Original-loan mode with a current balance entered: the payment M still comes from the original amount and term (a fixed-rate payment does not change), and the schedule runs forward from this month with the current balance.
Current-balance mode refuses a payment that does not exceed the first month's interest (balance x r), because the balance would never fall.
- Rounding
- Balances and interest are carried at full floating-point precision month to month; dollar figures are rounded to the cent for display only. Interest saved is the difference of the unrounded totals, so it can differ by a cent from subtracting the two rounded totals shown.
- Inputs used
- Start from: the original loan, or the current balance and monthly payment
- Annual interest rate, 0% to 50%
- Original-loan mode: original loan amount; term in years plus 0 to 11 months; loan start month (optional, defaults to this month); current outstanding balance (optional)
- Current-balance mode: current balance; current monthly payment (principal and interest)
- Extra monthly payment, and the month recurring extras start (optional, defaults to the loan start or this month)
- Extra yearly payment and the calendar month it is paid
- One-off extra payment and its month
- What this does not account for
- Escrow for property tax and insurance, PMI, and any fee: principal and interest only
- Daily interest accrual: interest is charged monthly on the balance, so a lender that counts days will differ slightly
- Precomputed-interest loans, where the CFPB notes extra payments do not reduce the interest owed
- Variable or adjustable rates: the rate entered holds for the whole loan
- Prepayment penalties, and lenders that hold extra money as 'paid ahead' instead of reducing the balance
- Recasting or refinancing: the regular payment never changes
- Jurisdiction
- United States conventions (USD, monthly amortising loans); the arithmetic itself applies to any fixed-rate loan with monthly payments.
- Source
- Consumer Financial Protection Bureau, "What's the difference between a simple interest rate and precomputed interest on an auto loan?"
- Effective date
- Not date-sensitive: the amortisation arithmetic does not change on a schedule. The CFPB pages cited were read on 24 September 2026.
- Version
- 2.0
- Last substantive review
- 2026-09-24
- Limitations
- CFPB describes simple interest (interest on the outstanding balance) and why extra payments reduce it; it publishes no amortisation formula to quote. The formula above is the standard fixed-payment annuity formula, checked against this tool's output independently (tools/page-generator/tests/test_extra_payment_cases.py).
- Dates are whole months: the payoff date is the month of the final payment, not a day.
- In current-balance mode the schedule starts this month, so the payoff month moves as time passes; the payment counts and interest do not.
- An estimate, not a loan payoff quote. The lender's payoff figure is the one that counts.
Reference cases
Five worked examples you can check by hand against the formula above.
Reference case 1: $20,000 at 6% over 5 years from January 2026, $100 extra every month
- Start from: Original loan
- Loan amount: $20,000
- Rate: 6%
- Term: 5 years
- Start: 2026-01
- Extra monthly: $100
Result: Regular payment $386.66. Payments: 60 without extras, 47 with. Total interest $3,199.36 without extras, $2,444.38 with. Interest saved $754.98. Payoff 2030-12 without extras, 2029-11 with.
Reference case 2: Same loan, $1,200 extra every December
- Start from: Original loan
- Loan amount: $20,000
- Rate: 6%
- Term: 5 years
- Start: 2026-01
- Extra yearly: $1,200 in December
Result: Regular payment $386.66. Payments: 60 without extras, 48 with. Total interest $3,199.36 without extras, $2,589.40 with. Interest saved $609.96. Payoff 2030-12 without extras, 2029-12 with.
Reference case 3: Same loan, one $1,200 lump sum in the first month
- Start from: Original loan
- Loan amount: $20,000
- Rate: 6%
- Term: 5 years
- Start: 2026-01
- One-off extra: $1,200 in 2026-01
Result: Regular payment $386.66. Payments: 60 without extras, 56 with. Total interest $3,199.36 without extras, $2,801.47 with. Interest saved $397.90. Payoff 2030-12 without extras, 2030-08 with.
Reference case 4: $300,000 mortgage at 6.5% over 30 years from January 2026, $200 extra every month
- Start from: Original loan
- Loan amount: $300,000
- Rate: 6.5%
- Term: 30 years
- Start: 2026-01
- Extra monthly: $200
Result: Regular payment $1,896.20. Payments: 360 without extras, 277 with. Total interest $382,633.47 without extras, $279,184.67 with. Interest saved $103,448.79. Payoff 2055-12 without extras, 2049-01 with.
Reference case 5: Current balance mode: $15,000 owed at 7%, paying $350 a month, $50 extra every month
- Start from: Current balance and payment
- Current balance: $15,000
- Rate: 7%
- Monthly payment: $350
- Extra monthly: $50
Result: Regular payment $350.00. Payments: 50 without extras, 43 with. Total interest $2,311.47 without extras, $1,977.16 with. Interest saved $334.31. Payoff months depend on the month you calculate in; the counts and interest do not.
Change log
| Date | Change |
|---|---|
| 2026-09-24 | Card published (T-820). Page rewritten: placeholder copy replaced, current-balance-and-payment mode added, plain-English result line, regular payment and payment counts shown, examples table, CFPB-sourced notes on simple interest, paid-ahead status and prepayment penalties; an unverified FAQ example removed. All five reference cases read from the live calculator (tests/figures/extra-payment-figures.spec.js) and recomputed independently in Python to the cent. |
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Disclaimer: This calculator provides estimates based on the information you enter. Actual savings and payoff dates may vary. Consult with a financial advisor for personalized advice.