Car Loan Calculator

Metric	Value	Copy
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Year	Principal Paid ($)	Interest Paid ($)	Ending Balance ($)	Copy
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Month	Principal ($)	Interest ($)	Payment ($)	Balance ($)	Copy
{{ r.period }}	{{ format(r.principal) }}	{{ format(r.interest) }}	{{ format(r.payment) }}	{{ format(r.balance) }}

Car loans are installment agreements that spread the cost of a vehicle across fixed monthly payments. A car loan amortization schedule explains how each payment shifts from interest toward principal over time. Understanding that pattern helps you compare offers and set a realistic budget.

Enter the purchase price you plan to finance and, if relevant, a down payment so the financed amount reflects your plan. Choose an annual rate and a term in years and months, then decide whether to add a small extra amount each month to shorten the payoff.

The results show the monthly payment, total interest across the term, and a projected finish date in your local time. You can compare scenarios by adjusting one input at a time and watching how the payment split and remaining balance change.

If the payment is smaller than the monthly interest, the balance will not fall and the app warns you to adjust rate, term, or extra amount. Use consistent units and realistic rates for clearer comparisons.

Choose this for a quick, transparent view of fixed rate auto financing. It does not model variable rates, fees, or balloon structures.

Technical Details:

The calculator models a fixed‑rate installment loan paid monthly. It treats the Annual Percentage Rate (APR) as a nominal yearly rate converted to a monthly periodic rate and computes a payment that exactly amortizes the financed principal.

From the principal P, monthly rate i, and total term n months, it first finds the base annuity payment and then adds any extra monthly prepayment E. When the APR is zero, payments are an even split of principal over the term. Adding E reduces total interest and shortens the payoff time.

Interpret results as steady, on‑time payments under a constant rate. Comparisons are most meaningful when you vary one factor at a time and keep others fixed.

\begin{array}{l} i & = & \frac{r}{12 \times 100} \\ A & = & \frac{P \times i}{1 - {(1 + i)}^{- n}} + E for i > 0 \\ A & = & \frac{P}{n} + E for i = 0 \end{array}

Symbols and units
Symbol	Meaning	Unit/Datatype	Source
P	Financed principal after down payment	$	Input/derived
r	Annual Percentage Rate (APR)	% per year	Input
i	Monthly periodic rate	decimal	Derived
n	Total number of months	months	Input
E	Extra monthly prepayment	$	Input
A	Total monthly payment (base plus extra)	$	Derived
I_k	Interest in month k (previous balance × i)	$	Derived
B_k	Ending balance after month k	$	Derived

Worked example. With P = $30,000, r = 4.5, n = 60, E = $0:

i = \frac{4.5}{12 \times 100} = 0.00375

A \approx \frac{30000 \times 0.00375}{1 - {(1 + 0.00375)}^{- 60}} \approx $ 559.31

Total interest = n \times A - P \approx $ 3558.54

Interpretation: about $559 per month, around $3,559 in interest, payoff in 60 months.

Units, precision & rounding policy

Displayed currency uses your locale’s decimal separator with two fraction digits.
Balances update each month; internal balance uses eight‑decimal rounding for stability.
APR is a nominal yearly rate; monthly rate is APR ÷ 12 ÷ 100.
Finish date is computed by adding payoff months to today in local time.

Validation & bounds (from code)

Validation rules extracted from the implementation
Field	Type	Min	Max	Step/Pattern	Error Text	Placeholder
Loan amount	number	0	—	0.01	Enter a positive loan amount.	—
Interest rate (APR)	number	0	—	0.01	Invalid or negative values are treated as 0.	—
Term years	integer	0	—	1	Term must be at least 1 month.	—
Term months	integer	0	11	1	Term must be at least 1 month.	—
Down payment	number	0	≤ Loan	0.01	Down payment equals or exceeds loan amount; nothing to finance.	—
Extra monthly	number	0	—	0.01	Payment does not cover monthly interest. Increase payment or reduce rate/term.	—
Iteration cap	months	—	1200	—	Computation limited to 1200 months. Balance remains.	—

I/O formats

Inputs and outputs
Input	Accepted Families	Output	Encoding/Precision	Rounding
Loan, rate, term, down, extra	Numeric fields	Payment, totals, payoff date	2 decimal display	Locale currency rounding
—	—	Annual schedule	CSV copy/download	Raw numbers
—	—	Monthly schedule	CSV copy/download	Raw numbers
—	—	Payload	JSON copy/download	Pretty‑printed

Networking & storage

All calculations run in the page; no server requests are made for your inputs.
A charting layer is loaded by the host; results are rendered locally.
Clipboard and file downloads are user‑initiated and keep data on your device.

Performance & determinism

Time complexity is linear in the number of months simulated.
Identical inputs produce identical schedules and totals.

Assumptions & limitations

Heads‑up APR is nominal; compounding is monthly only.
No origination fees, taxes, or insurance are included.
Payments are equal and on time; no late or skipped payments.
Extra payment is constant each month and applied to principal.
Zero‑rate loans amortize linearly over the term.
Finish date uses today’s local calendar; it is an estimate, not a due date.
Terms longer than 1200 months are not simulated.
Variable rates, balloons, and irregular first periods are out of scope.

Edge cases & error sources

Amounts at or below zero yield no schedule.
Down payment equal to the loan leaves nothing to finance.
Term of zero months is invalid.
Very small payments may not cover interest and halt the run.
Large values can accumulate floating‑point rounding differences.
Different locales show different decimal separators in display only.
Entering months above 11 is clamped to 11.
Finish date near month‑end adjusts to the month’s last valid day.
Charts may not render if the charting layer fails to load.
Copy/download relies on clipboard and file APIs available in your browser.

Privacy & compliance

No data is transmitted or stored server‑side. Outputs are educational and not financial advice.

Step‑by‑Step Guide:

Estimate fixed car‑loan payments and totals in a few steps.

Enter the Loan amount.
Enter the Interest rate (APR).
Set Years and Months.
Optionally add a Down payment.
Optionally add an Extra monthly amount.
Review payment, totals, payoff months, and the schedule.

Example: 30,000 at 4.5 for 5 years gives about $559 per month. Adding $50 extra shortens the term and lowers interest.

Copy or download schedules when you are satisfied with a scenario.

FAQ:

Is my data stored?

No. Calculations run locally and nothing is sent to a server.

Clipboard and downloads occur only when you ask.

How accurate is the payment?

It uses the standard annuity formula with monthly compounding and eight‑decimal internal balance updates; displayed values round to two decimals.

Which fields and formats are supported?

Numeric inputs for amount, APR, years, months, down payment, and extra monthly. Output includes payment, totals, payoff date, and amortization tables.

Can I include fees or taxes?

Not directly. To approximate, add them into the loan amount or down payment based on how you plan to finance them.

Does it work offline?

Yes after the page loads. Charts may not appear if the chart layer is unavailable offline; tables and totals still compute.

How do I calculate payment by hand?

Convert APR to a monthly rate, apply the annuity formula shown above, then add any extra monthly amount to get the total payment.

What does the warning about interest mean?

If the payment is less than the monthly interest, the balance will not decrease. Increase payment or reduce rate or term.

Can I model a balloon or variable rate?

No. This calculator assumes equal monthly payments and a constant rate for the entire term.

Troubleshooting & Glossary:

Numbers not accepted: ensure values are non‑negative and months are 0 to 11.
No results: confirm loan amount > 0 and term > 0 months.
Payment seems high: reduce APR or extend the term to compare.
Finish date looks odd: month‑end dates adjust to the last valid day.
Chart is blank: switch tabs or try again after the chart layer loads.
CSV opens with commas as decimals: adjust your spreadsheet’s locale settings.

Payment does not cover monthly interest. Increase the payment or reduce rate or term to avoid a growing balance.

Glossary

Principal: Amount financed after any down payment.
APR: Annual Percentage Rate, a yearly nominal interest rate.
Amortization: Gradual repayment of principal through scheduled payments.
Prepayment: Extra money applied to principal beyond the required amount.
Term: Total number of months in the repayment plan.
Periodic rate: Monthly rate derived from APR.
Negative amortization: When payments do not cover interest and the balance grows.