Loan Calculator — Monthly Payment & Amortization

What this loan calculator does

This English-language loan calculator applies the standard PMT formula to compute your fixed monthly payment, total interest paid over the life of the loan, and a complete amortization schedule — one row per payment, showing exactly how each dollar splits between principal and interest. It works for auto loans, personal loans, student loans, and the principal-and-interest portion of a mortgage. It is honest about its scope: taxes, insurance, PMI, and HOA fees are not included here, because those belong in a dedicated mortgage calculator. What you get is the clean math of principal plus interest, nothing more. The tool also models extra monthly principal payments, which can have a dramatic effect — even $50 extra per month on a 30-year, $300,000 loan at 6.5% saves tens of thousands in interest and shaves years off the payoff date. The [compound interest calculator](/en/compound-interest-calculator/) on this site shows the same compounding effect from the investment side, which is useful when you are deciding whether to pay down debt faster or invest the difference. Everything runs in your browser: 100% client-side — your data never leaves your browser. No uploads, no tracking, no server logs.

Features

Standard PMT formula. Uses the same fixed-rate amortization formula found in every spreadsheet and financial textbook, so results match what your lender will quote.
Full amortization schedule. Every payment row shows the date, total payment, principal portion, interest portion, and remaining balance — useful for tax records or loan comparisons.
Extra principal payments. Enter an optional extra monthly principal amount to see how early payoff changes your total interest and payoff date in real time.
Auto loan and car payment estimation. Works equally well as a car loan calculator or auto loan calculator. Enter the financed amount, dealer APR, and term to get your estimated car payment instantly.
Honest scope — P+I only. The calculator clearly separates principal and interest from escrow items. For a full housing payment estimate, pair it with the [Mortgage Refinance Calculator](/en/mortgage-refinance-calculator/).
Privacy by design. No data is sent to any server. The calculation runs entirely in your browser using client-side JavaScript, so sensitive financial figures stay on your device.

How to use the loan calculator

Fill in four fields and the result appears immediately — no form submission required.

Enter the loan amount. Type the principal you are borrowing — for example, 300000 for a $300,000 mortgage or 25000 for a car loan.
Set the annual interest rate. Enter the nominal APR your lender quoted, such as 6.5. Note that APR is a nominal rate; the effective annual cost compounds slightly higher due to monthly compounding.
Choose the loan term. Enter the repayment period in years: 30 for a standard mortgage, 5 for a typical auto loan, or any custom value.
Optionally add extra monthly payments. Enter any amount you plan to pay above the required payment each month. The payoff date and total interest fields update immediately to reflect the savings.
Expand the amortization schedule. Click "Show amortization schedule" to see the full payment-by-payment breakdown, which you can scroll or copy for your records.

Common use cases

Comparing two loan offers. Run the calculator twice with the rates from two different lenders. A 0.25% difference on a $400,000 loan over 30 years can exceed $20,000 in total interest — the amortization schedule makes this concrete.
Estimating a car payment before the dealership. Use the auto loan calculator mode before visiting the dealer in Austin or Seattle. Knowing your expected payment on the financed amount helps you negotiate from a position of clarity rather than reacting to a monthly payment pitch.
Evaluating extra principal payments vs. investing. Put $200/month extra into the loan and note the interest saved. Then compare that figure against projected returns using the [Investment ROI Calculator](/en/investment-roi-calculator/) to decide which use of cash wins on your timeline.
Modeling a refinance to a shorter term. Enter your remaining balance, new rate, and a 15-year term to see whether the higher monthly payment is worth the reduction in total interest — a common question for homeowners 5–10 years into a 30-year mortgage.
Understanding amortization for first-time buyers. New buyers are often surprised that early payments are almost entirely interest. The month-by-month schedule makes that front-loading visible and helps set realistic expectations about building equity.

Frequently asked questions

Does this calculator include taxes and insurance?

No — and that is intentional. This tool calculates pure principal and interest (P+I). Property taxes, homeowner's insurance, PMI, and HOA fees vary by location and lender escrow requirements. Adding them here would make the output misleading for personal loans and auto loans, which have none of those costs. Use this for the debt math, then add escrow estimates separately for a full housing budget.

Is my financial data private?

Yes. The entire calculation runs in your browser using client-side JavaScript. No loan amount, rate, or personal detail is transmitted to any server. There are no cookies set, no analytics tied to your inputs, and no server logs of any kind. You can even disconnect from the internet after the page loads and the calculator will still work.

Why does my lender's quoted payment differ slightly from this result?

The most common reason is rounding — lenders often round to the nearest cent at each step. A second reason is that the APR your lender advertises may include origination fees amortized into the rate, making the effective cost marginally higher than the nominal rate you entered. A third scenario is an adjustable-rate loan (ARM), where the rate — and therefore the payment — resets at each adjustment period. This calculator models fixed-rate loans only; for ARMs, you would re-run it at each new rate.

Is a huge tax refund related to loans in any way?

Indirectly, yes. When you over-withhold federal taxes all year, you are effectively giving the government an interest-free loan until your refund arrives. That "lost" interest is the same compounding logic this calculator models — money that could have reduced your loan balance each month instead sits idle. Adjusting your W-4 withholding to break even and directing the difference to extra principal payments is one of the most straightforward ways to cut total interest paid.

How do extra monthly principal payments affect total interest?

Even small additions to the principal payment compound in your favor. Because interest each month is calculated on the outstanding balance, reducing that balance faster means less interest accrues at every subsequent payment. The effect is non-linear: an extra $100/month on a 30-year loan can save several years of payments and a disproportionate amount of total interest — the amortization schedule shows exactly where the lines diverge.

Can I use this as a mortgage calculator?

Yes, for the principal-and-interest component. Enter your loan amount, the fixed note rate (not the APR with fees), and the term in years. What you get is the core P+I payment that your lender uses to qualify you under debt-to-income rules. Student loan balances also affect mortgage approvals — a widely overlooked factor when buyers are surprised during underwriting. For a full refinance comparison including closing costs, the [Mortgage Refinance Calculator](/en/mortgage-refinance-calculator/) covers that scenario.