How to Calculate Loan Payments (Free Loan Calculator)

Before you sign for a personal, car or student loan, it pays to know exactly what each month will cost and how much interest you will hand over in total. The advertised monthly figure rarely tells the whole story. This guide explains the loan payment formula, shows a real example, and points out the traps to avoid. To get instant numbers without the maths, use the free Loan Calculator — it shows your monthly payment, total interest and total repayment, and runs entirely in your browser.

The loan payment formula

Most installment loans are amortized, meaning you pay a fixed amount each month that covers interest plus a shrinking slice of the balance. The formula is the same one used for mortgages:

M = P x r x (1 + r)^n / ((1 + r)^n - 1)

Where:

• M is the monthly payment
• P is the amount borrowed
• r is the monthly interest rate (annual rate / 12)
• n is the number of monthly payments (years x 12)

The longer the term, the lower the monthly payment but the more total interest you pay.

How to use the Loan Calculator

You do not need a spreadsheet:

1. Open the Loan Calculator.
2. Enter the loan amount.
3. Enter the annual interest rate (APR).
4. Enter the term in months or years.
5. Read your monthly payment, total interest and total repayment instantly.

Adjust any field and the figures recalculate, so you can see how a shorter term or lower rate changes the cost.

A worked example

Imagine a 20,000 car loan at 7% APR over 5 years (60 months).

• P = 20,000
• r = 0.07 / 12 = 0.005833
• n = 60

The monthly payment works out to about 396. Across 60 payments you repay roughly 23,761, so the interest is about 3,761. Stretch the same loan to 7 years and the monthly payment falls to around 302, but the total interest climbs to about 5,360 — paying less each month costs you more in the end.

Common types of loan

The same formula applies whether the loan is for a car, a home improvement, or tuition:

Always compare the APR rather than the headline rate, since APR includes fees and gives a truer cost.

Tips and mistakes to avoid

Keep more of your money with these:

• Focus on total cost, not just the monthly payment — a low payment can hide a long, expensive term.
• Check for prepayment penalties before paying a loan off early.
• A higher credit score usually earns a lower rate; even 1% matters.
• Borrow only what you need; a smaller principal means smaller interest.

For home loans specifically, use the Mortgage Calculator, and for equated monthly installments common in some regions, try the EMI Calculator.

How the term changes the cost

Lengthening a loan lowers the monthly payment but quietly raises the total interest, because you are borrowing the money for longer. The table below takes the same 20,000 loan at 7% APR and varies only the term.

Stretching from 3 to 7 years roughly halves the monthly payment but more than doubles the interest. A longer term can be the right call if it keeps the payment affordable, but go in knowing the trade: lower monthly cost almost always means a higher total cost.

Secured versus unsecured loans

Loans fall into two broad groups, and the difference shapes your rate. A secured loan is backed by collateral — a car backs an auto loan, a house backs a mortgage. Because the lender can repossess the asset if you default, secured loans usually carry lower interest rates. An unsecured loan, such as most personal loans and credit cards, has no collateral, so the lender takes on more risk and charges a higher rate to compensate.

That is why a personal loan at the same credit profile often costs several percentage points more than an auto loan. When you compare offers, make sure you are comparing like with like: a low advertised rate may apply only to secured borrowing or only to the strongest credit scores. Use the Loan Calculator with the actual APR you are quoted, not the headline teaser rate.

What affects the interest rate you are offered

Lenders set your rate by estimating how likely you are to repay. The main factors:

• Credit score. The single biggest lever; a strong score can shave several points off your APR.
• Loan term. Shorter terms often come with lower rates as well as lower total interest.
• Loan amount and type. Very small or very large loans, and unsecured loans, can carry higher rates.
• Income and debt-to-income ratio. Lenders want to see that the new payment fits comfortably alongside your other obligations.
• Down payment or collateral. Putting more down on a secured loan lowers the lender's risk and can lower your rate.

Improving even one of these before you apply — paying down a card to lift your score, for instance — can meaningfully reduce what you pay over the life of the loan.

Is it free and private?

Yes. The Loan Calculator is free, requires no account, and runs every calculation locally in your browser, so nothing you enter leaves your device. Use it as a planning estimate and confirm exact figures with your lender. Find more free calculators or browse all tools.