What is the difference between APR and the interest rate I should enter?

The contractual interest rate drives the amortization of principal. APR can package certain fees and insurance into an annualized comparison figure. For payment math, use the note rate; for shopping cost of credit, also read the APR and fee table on the disclosure.

Does this work for auto loans and personal loans?

Yes for standard fixed-rate loans with equal monthly payments. Revolving cards, HELOCs with draws, and loans that reamortize after a promotional period need different modeling.

Why is my bank or dealer payment a few cents different?

Rounding to the nearest cent, odd first/last periods, and day-count methods create tiny gaps. If the gap is large, check for prepaid finance charges rolled into principal or a different term length.

Can I model a variable-rate loan?

This calculator locks a single rate for the whole term. For variable products, run today’s rate for a baseline, then re-run when the rate resets so you see the new payment before it hits your budget.

How do I include a down payment?

Subtract the down payment (and any trade equity you apply) from the cash price, then enter only the financed remainder as principal. Do not enter the full sticker price if part of it is paid upfront.

Should I finance taxes and warranties?

You can, but financing extras raises principal and total interest. Run one scenario with them rolled in and one without so you see the monthly and lifetime cost of financing add-ons.

What if my loan has a balloon payment?

A balloon leaves a large principal due at the end and is not the same as a fully amortizing schedule. Use a dedicated balloon structure or ask the lender for the amortization printout rather than forcing this equal-payment formula.

How do extra payments change the result?

The baseline assumes you pay only the scheduled amount. Extra principal typically shortens the term or lowers later interest; confirm whether your lender applies extras immediately to principal and whether fees apply.

Is a longer term always a worse deal?

Longer terms lower the monthly payment but usually increase total interest. A longer term can still be rational if the monthly cash frees you to clear higher-interest debt first—just measure both payment and total interest.

Can I use this for a credit card balance?

Only as a rough “if I paid it like a fixed installment” experiment. Card minimums, variable APRs, and new charges mean actual payoff dates differ from this fixed schedule.

What happens if I pay late?

Late fees and possible rate penalties sit outside this formula. Always read your note for grace periods; the calculator assumes on-time equal payments.

Do you store the loan amounts I enter?

No. Math runs locally in your browser session. Still avoid pasting full account numbers into any web form when a private spreadsheet or lender portal is more appropriate for sensitive identifiers.

Loan Calculator

Use this loan calculator when you need a straightforward monthly payment and total-interest estimate for a fixed-rate installment loan—auto financing, personal loans, or similar products with equal periodic payments. Enter how much you borrow, the annual interest rate, and the term length, then compare quotes without mixing different fee assumptions. It shows the baseline schedule if you pay as agreed; it does not underwrite your credit, model revolving credit-card minimums, or absorb dealer add-ons into APR unless you fold those costs into the principal yourself. Treat outputs as planning math, not a signed contract.

Monthly payment

$395.08

Total paid

$23,704.86

Total interest

$3,704.86

For estimates only.

Informational only; verify critical results independently.

How to use

Enter the principal you will actually finance after any down payment or trade-in credit—leave optional warranties and dealer fees out unless you plan to roll them into the loan balance.
Type the nominal annual interest rate as a percent (for example, 7.9 for 7.9%), matching the rate on the loan contract rather than a marketing APR if fees make APR different.
Set the repayment term in months or years exactly as the lender quotes it; a 60-month auto loan is five years, while many personal loans use 24–84 month schedules.
Read the scheduled monthly payment first, then check total interest over the full term so you see the true cost of stretching payments out.
Compare two lender offers by holding principal constant and changing only rate or term, which keeps the comparison fair.
If one quote includes prepaid fees financed into the note, increase principal by those fees and recalculate so you are not comparing an “out-the-door” loan to a leaner one.
Test a shorter term on the same principal and rate to see how much monthly cash flow you would need to cut total interest.
For used-auto shopping, re-run the model with a slightly higher rate to reflect possible credit-tier pricing before you fall in love with a payment target.
Remember that extra principal payments outside this baseline schedule can shorten the loan; ask the lender how they apply extras before assuming an early payoff date.
Bring the winning scenario to the disclosure paperwork and verify first-payment date, late fees, and any prepayment rules that this simple amortization view does not encode.

Examples

$20,000 auto loan at 7% for 5 years (60 months) ≈ $396/mo; total interest about $3,760 if paid as scheduled.
$10,000 personal loan at 11.5% for 3 years ≈ $330/mo; total interest roughly $1,880 over 36 payments.
$35,000 at 6.5% for 72 months ≈ $588/mo; extending the same deal to 84 months drops payment to about $519/mo but raises total interest.
$15,000 at 5.9% for 48 months ≈ $351/mo versus about $288/mo on a 60-month term at the same rate—lower payment, higher lifetime interest.
$8,500 at 9.25% for 36 months ≈ $271/mo; paying it off in 24 months instead at the same rate would need about $389/mo.
Dealer quote: $28,400 financed at 8.2% for 72 months ≈ $498/mo; adding $1,200 of rolled fees ($29,600) lifts payment to about $519/mo.
$5,000 home-improvement installment at 8% for 7 years (84 months) ≈ $78/mo with roughly $1,550 in total interest.
Compare $12,000 at 4.9% for 36 months (≈ $359/mo) versus 48 months (≈ $276/mo) when choosing a promo financing window.
$22,000 at 6.99% for 60 months ≈ $436/mo; a half-point higher rate (7.49%) raises payment to about $441/mo—small monthly change that still adds interest over five years.
Student-style consolidation illustration: $40,000 at 6.25% for 10 years ≈ $449/mo with about $13,880 in interest if the rate stays fixed.

FAQ

What is the difference between APR and the interest rate I should enter?: The contractual interest rate drives the amortization of principal. APR can package certain fees and insurance into an annualized comparison figure. For payment math, use the note rate; for shopping cost of credit, also read the APR and fee table on the disclosure.
Does this work for auto loans and personal loans?: Yes for standard fixed-rate loans with equal monthly payments. Revolving cards, HELOCs with draws, and loans that reamortize after a promotional period need different modeling.
Why is my bank or dealer payment a few cents different?: Rounding to the nearest cent, odd first/last periods, and day-count methods create tiny gaps. If the gap is large, check for prepaid finance charges rolled into principal or a different term length.
Can I model a variable-rate loan?: This calculator locks a single rate for the whole term. For variable products, run today’s rate for a baseline, then re-run when the rate resets so you see the new payment before it hits your budget.
How do I include a down payment?: Subtract the down payment (and any trade equity you apply) from the cash price, then enter only the financed remainder as principal. Do not enter the full sticker price if part of it is paid upfront.
Should I finance taxes and warranties?: You can, but financing extras raises principal and total interest. Run one scenario with them rolled in and one without so you see the monthly and lifetime cost of financing add-ons.
What if my loan has a balloon payment?: A balloon leaves a large principal due at the end and is not the same as a fully amortizing schedule. Use a dedicated balloon structure or ask the lender for the amortization printout rather than forcing this equal-payment formula.
How do extra payments change the result?: The baseline assumes you pay only the scheduled amount. Extra principal typically shortens the term or lowers later interest; confirm whether your lender applies extras immediately to principal and whether fees apply.
Is a longer term always a worse deal?: Longer terms lower the monthly payment but usually increase total interest. A longer term can still be rational if the monthly cash frees you to clear higher-interest debt first—just measure both payment and total interest.
Can I use this for a credit card balance?: Only as a rough “if I paid it like a fixed installment” experiment. Card minimums, variable APRs, and new charges mean actual payoff dates differ from this fixed schedule.
What happens if I pay late?: Late fees and possible rate penalties sit outside this formula. Always read your note for grace periods; the calculator assumes on-time equal payments.
Do you store the loan amounts I enter?: No. Math runs locally in your browser session. Still avoid pasting full account numbers into any web form when a private spreadsheet or lender portal is more appropriate for sensitive identifiers.

Formula / Method

Monthly payment uses standard amortization: with principal P, monthly rate r = annual rate/12, and n months, payment = P × [r(1+r)^n]/[(1+r)^n − 1]. When r is zero, payment is simply P/n. Total interest equals (payment × n) − P for a loan paid exactly on schedule with no extras.

Assumptions & Limitations

Models a fixed rate and fixed payment schedule only. It ignores credit underwriting, deferred interest promotions, simple-interest day counts that diverge from monthly compounding assumptions, and balloon or interest-only structures. Figures are estimates for comparison—not credit offers or legal advice.

Related guides

Mortgage and Loan Basics: What You Need to Know
Estimate mortgage and loan payments from principal, rate, and term—plus tax, insurance, and interest trade-offs with free calculators.

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Last updated: 2026-07-13

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