Enter the loan amount, annual interest rate and term to instantly calculate your monthly payment, total payment and total interest.
This calculator uses the formula behind almost every mortgage and auto loan worldwide: fixed-payment amortization. Your monthly payment M is M = P × r × (1+r)^n / ((1+r)^n − 1), where P is the principal, r is the monthly interest rate (annual rate ÷ 12 ÷ 100), and n is the total number of payments (years × 12). The logic behind it: the lender solves for the one fixed monthly amount that will pay off both the principal and all accrued interest in exactly n payments. Because the payment is fixed but the outstanding balance shrinks over time, the interest portion of each payment (balance × monthly rate) shrinks too — which is exactly why early payments on a 30-year mortgage are mostly interest, while later payments are mostly principal.
Many borrowers pick a loan purely based on "can I afford the monthly payment," while ignoring total interest cost. Stretching the term lowers the monthly payment but increases total interest, because the balance stays higher for longer. For example, borrowing 1,000,000 at 2.2% over 30 years costs about 3,807/month with roughly 370,000 in total interest; shortening it to 20 years raises the payment to about 5,159/month (about 1,352 more per month) but cuts total interest to roughly 238,000 — over 130,000 less. When comparing loan offers, look at both numbers: whether the monthly payment fits your budget, and the total interest cost. This tool's result table deliberately separates "Total Payment" from "Total Interest" so that trade-off is visible at a glance.
Say P = 500,000, annual rate 2.1%, term 30 years. First, the monthly rate: r = 2.1 ÷ 100 ÷ 12 ≈ 0.00175. Total payments: n = 30 × 12 = 360. Plugging into the formula: (1+r)^n ≈ (1.00175)^360 ≈ 1.887, so M = 500,000 × 0.00175 × 1.887 ÷ (1.887 − 1) ≈ 500,000 × 0.00175 × 1.887 ÷ 0.887 ≈ 1,864. That's roughly 1,864 per month; over 360 payments the total comes to about 671,000, meaning total interest is about 171,000 — nearly a third of the original principal. This is why a 0.1%–0.2% rate difference, which looks tiny on paper, adds up to a real amount of money over a 30-year term.
The five built-in loan-type presets reflect real-world risk pricing: mortgages are secured by real estate and carry low default risk, so they get the longest terms (up to 30 years) and lowest rates; personal loans are unsecured and priced almost entirely on the borrower's credit, hence the much wider and higher rate range (roughly 5%–16%); auto loans reflect vehicle depreciation, and student loans often carry policy-subsidized rates. These presets are market-reference values only — your actual approved rate depends on the lender's underwriting of your credit profile and collateral.
This tool always uses fixed-payment amortization (equal monthly installments), which is the standard default for most mortgages and auto loans. If your actual loan uses fixed-principal repayment (where the principal portion is constant and the total payment shrinks over time), your real numbers will differ — check your lender's official amortization schedule.
Entering 0 for the interest rate is handled correctly — the tool simply divides the loan amount by the number of months to get a pure principal-only payment. However, entering 0 or a negative number for the term makes amortization undefined, so the result section is hidden until you enter a term of at least 1 year.
No. This calculator only computes the standard principal-plus-interest amortized payment. It does not include origination fees, account maintenance fees, loan-linked insurance, or prepayment penalties, which vary by lender and product. For your true total cost, refer to your lender's official loan disclosure documents.
Nothing is sent anywhere. All calculations run instantly in your browser using JavaScript — there is no fetch call or network request that transmits the amount, rate, or term you enter to any server, and nothing is saved once you reload the page. It's safe to enter your actual loan figures.
Switching the loan type dropdown (e.g. from Mortgage to Auto Loan) automatically fills in that type's typical rate and term for quick estimates. If you want to keep your own numbers, just re-enter them in the rate and term fields after switching — the result updates instantly.