United States version
How it works
Compare remaining cash payments under the current loan with a new term, keeping financed fees separate from up-front fees.
This is the United States planning view, with monetary inputs and outputs in USD. A currency label does not establish that a tax rate, construction price, coverage rule or legal limit has been verified locally. The inputs and limitations below describe the actual scope.
Input query strings and outputs
Use an input name in this page’s URL as ?name=value, and join additional inputs with &. Portable shared links may instead use the compact ?ac= state parameter.
Input query strings
7-
?balance=Current principal balanceMoney · Required · Default: 18,000
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?oldRate=Current annual nominal interest ratePercentage · Required · Default: 8
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?oldMonths=Current remaining monthly paymentsNumber · Required · Default: 48
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?newRate=New annual nominal interest ratePercentage · Required · Default: 5
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?newMonths=New term, monthly paymentsNumber · Required · Default: 48
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?fees=Refinance feesMoney · Required · Default: 300
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?financeFees=Add fees to the new principalTrue or false · Optional · Default: false
Outputs
5-
oldPaymentCurrent modeled monthly paymentCurrency · Currency: USD
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newPaymentNew modeled monthly paymentCurrency · Currency: USD
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monthlySavingMonthly payment reductionCurrency · Currency: USD
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totalSavingDifference in remaining total cash paidCurrency · Primary output · Currency: USD
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feePaybackUp-front fee payback, monthsNumber
Formula
level payment = principal × monthly rate / (1 − (1 + monthly rate)^−months).
Calculations retain numeric precision internally. Displayed values are rounded for readability. Quantities that must be purchased as whole units are rounded up only where the formula explicitly requires it.
Read the inputs before calculating
- Current principal balance: Enter the quantity described by the label.
- Current annual nominal interest rate: Enter the quantity described by the label.
- Current remaining monthly payments: Enter the quantity described by the label.
- New annual nominal interest rate: Enter the quantity described by the label.
- New term, monthly payments: Enter the quantity described by the label.
- Refinance fees: Enter the quantity described by the label.
- Add fees to the new principal: Enter the quantity described by the label. Leave this unconfirmed until you have actually checked the required condition.
Reproducible worked example
The following is a fictional arithmetic example, not a local quote, a verified claimant or a market forecast. Its values are included so the formula can be checked. The form does not automatically confirm any verification checkbox.
| Input | Example value |
|---|---|
| Current principal balance | 18,000 |
| Current annual nominal interest rate | 8 |
| Current remaining monthly payments | 48 |
| New annual nominal interest rate | 5 |
| New term, monthly payments | 48 |
| Refinance fees | 300 |
| Add fees to the new principal | false |
| Output | Calculated result |
|---|---|
| Current modeled monthly payment | USD 439.4326 |
| New modeled monthly payment | USD 414.5273 |
| Monthly payment reduction | USD 24.9053 |
| Difference in remaining total cash paid | USD 895.4553 |
| Up-front fee payback, months | 12.0456 |
Interpreting a changed assumption
Start with one complete scenario and change only one input when diagnosing a difference. Recheck units, the period of every rate, whether an amount is recurring or one-off, and whether a cost is already included elsewhere. A larger calculated benefit is not evidence that an assumption is more likely to occur.
Limitations
- This uses entered contract assumptions. It is not lending approval, personalized financial advice or a substitute for the actual fee schedule and local credit/tax rules.
- A lower payment can cost more over a longer term. The nominal rate is not an APR including all fees, and daily interest or prepayment penalties require the contract.
Frequently asked questions
What does this Auto Refinance result represent?
Compare remaining cash payments under the current loan with a new term, keeping financed fees separate from up-front fees. It applies the displayed formula to your inputs; it does not infer omitted facts.
Are the starting amounts verified United States prices or legal rules?
No. Numeric defaults are illustrative unless an input or dated reference explicitly identifies a researched component. Currency is USD; local quotes, eligibility and unsupported rules must be entered and verified separately.
What must I check before relying on the result?
This uses entered contract assumptions. It is not lending approval, personalized financial advice or a substitute for the actual fee schedule and local credit/tax rules.
Can I compare or share different assumptions?
Change one assumption at a time and use the browser-local project or share controls. A shared URL contains the encoded input values; do not include information you do not wish to disclose.
Sources and reference scope
- CFPB loan-estimate explanation — retrieved 2026-09-24. US cost components; the general amortization formula is stated separately.
- CFPB comparing borrowing costs — retrieved 2026-09-24. Distinguishing interest, principal, fees and timing in a comparison.
These references support only their stated scope. They are not evidence that every local rule or price needed by the master expansion has been loaded.