Loan Calculator

Loan calculator — free and private

Before taking on a loan it helps to know what the monthly payment will be and how much it costs in total. This calculator does the arithmetic instantly: enter the amount, the annual interest rate, and the term, and it shows the fixed monthly payment, the total interest, and the total you will have paid by the end. Everything is worked out in your browser, so the figures you type never leave your device.

This is a math tool, not financial advice. It shows what the standard formula produces for the numbers you enter — useful for comparing options and planning a budget. A lender's exact figures can differ once fees, rounding, and their specific compounding rules are applied.

How an amortized payment works

Most everyday loans — car loans, personal loans, mortgages — are "amortized," meaning you pay the same amount every month and the loan is fully cleared by the end of the term. Each payment is split between interest on the remaining balance and a piece of the principal. Early on, most of the payment goes to interest because the balance is large; over time the balance shrinks, so more of each payment chips away at the principal.

The fixed monthly payment comes from the annuity formula: the payment is set so that, at the given monthly interest rate, the balance reaches exactly zero after the last payment. The monthly rate is simply the annual rate divided by twelve. When the interest rate is zero, there's no interest to spread, so the payment is just the amount divided by the number of months.

What affects the total interest

Three inputs drive everything. A larger amount means more interest, all else equal. A higher rate increases both the monthly payment and the total interest. The term is the interesting one: a longer term lowers the monthly payment, which can make a loan feel more affordable, but because the balance is carried for more months, the total interest usually goes up. The calculator shows the monthly payment and the total interest side by side, so the trade-off between a comfortable payment and a lower overall cost is easy to see.

Why it's worth calculating

Seeing the numbers before you commit turns a vague sense of "affordable" into concrete figures. You can test how a slightly shorter term changes the total cost, what a lower rate would save, or how much the monthly payment moves if you borrow a bit less. Running a few scenarios takes seconds and makes it easier to choose a loan that fits your budget. If you want to work out a rate change or a percentage difference on its own, the Percentage Calculator handles that, also entirely in your browser.

Works on your phone

The calculator is built mobile-first and runs in your phone's browser with nothing to install. The number fields bring up the numeric keypad, you can switch the term between years and months with a tap, and the results appear right below without any scrolling. Pick a currency symbol, or none, to match where you are.

Privacy: your numbers never leave your device

Every figure is calculated locally in your browser. The amounts and rate you enter are never uploaded, never stored on a server, and there's no account to create. When you close the page the numbers are gone, because they were never sent anywhere in the first place — which matters when you're sketching out something as personal as your finances.

Frequently asked questions

How is the monthly payment calculated?

With the standard amortized-loan formula, using the amount, the annual rate, and the term in months. The payment is fixed so the loan is fully paid off by the end. It's an estimate — a lender's exact figure may differ with fees.

What is total interest (the overpayment)?

The sum of all interest over the life of the loan — the difference between the total of every payment and the amount you borrowed.

Does a longer term mean paying more interest?

Usually yes. A longer term lowers each payment but spreads the balance over more months, so more interest accrues overall.

Is my data uploaded to a server?

No. Everything runs in your browser — the numbers you enter never leave your device, and nothing is stored or sent anywhere.