Mortgage Loan Calculator.
Calculate your monthly mortgage payment, total interest, and full cost of ownership. Built on the standard amortization formula used by lenders worldwide.
A down payment of 20% or more avoids private mortgage insurance (PMI).
Updates instantly as you type. No data is sent to a server.
How to Use This Calculator
1. Enter the Home Value — the agreed purchase price of the property. 2. Adjust the Down Payment percentage. The cash and remaining loan amounts update instantly underneath. 3. Set the Interest Rate. If you have a quote in hand, enter it; otherwise use the current 30-year fixed average for your country. 4. Pick a Loan Term. 15-year loans cost less in total but require larger monthly payments; 30-year loans flip that trade-off.
The Estimated Monthly Payment, Total Interest and Total Cost figures recalculate in real time as you adjust any input.
The Mathematical Foundation
M = P [ i(1 + i)^n ] / [ (1 + i)^n − 1 ] Where: M = Monthly payment P = Principal loan amount (home value − down payment) i = Monthly interest rate (annual rate ÷ 12 ÷ 100) n = Number of monthly payments (loan term in years × 12) This is the standard fixed-rate amortization formula. It does not include property taxes, homeowner's insurance, HOA fees, or PMI — those are typically escrowed separately and depend on location.
Worked Examples
Example 1 — A $450,000 home with 20% down ($90,000), a 6.75% APR and a 30-year term. Loan amount: $360,000. Monthly payment: ≈ $2,334.88. Total interest over 30 years: ≈ $480,557.
Example 2 — Same home, same rate, 15-year term. Monthly payment jumps to ≈ $3,184.69, but total interest drops to ≈ $213,243 — a savings of more than $267,000 over the life of the loan.
Example 3 — Increase the down payment from 20% to 25% on the 30-year scenario above and the monthly payment falls to ≈ $2,189.10, saving roughly $52,500 over 30 years.
Background
A mortgage is more than just a loan — it's a long-term structural commitment that compounds across decades. Use this calculator to strip away marketing jargon and see the true cost of your real estate purchase. The amortization process means your early payments are mostly interest, while principal reduction accelerates over time.
Whether you're buying your first home or refinancing an investment property, knowing the exact monthly payment, total interest, and break-even point helps you make a confident, evidence-based decision.
Small shifts in rate, term, or down payment can change lifetime borrowing costs by tens or even hundreds of thousands of dollars. Running multiple scenarios before you sign gives you negotiating power with lenders and helps you choose a payment that stays sustainable during changing market conditions.
Frequently Asked Questions
What is Private Mortgage Insurance (PMI)?
PMI is typically required if your down payment is less than 20% of the home's value. It protects the lender — not you — in case of default. PMI usually adds 0.3%–1.5% of the loan amount per year to your payment.
Should I choose 15 or 30 years?
A 15-year term offers lower interest rates and dramatically less total interest paid, but the monthly payment is roughly 35–50% higher. A 30-year term is more flexible and easier to qualify for, but you pay substantially more interest over the life of the loan.
How does the interest rate affect my buying power?
Every 1% increase in the interest rate reduces your buying power by roughly 10% for the same monthly payment. Locking in a low rate when one is available can be more valuable than negotiating the purchase price.
Are taxes and insurance included in this calculation?
No. This calculator returns Principal & Interest only — the deterministic part of your payment. Property taxes, homeowner's insurance, HOA fees and PMI vary by location and lender. Add them as separate line items in your budget.
Can I trust this calculator?
Yes — every number is computed locally in your browser using a deterministic math engine (mathjs), with no eval() and no third-party scripts. The same formula is used by major US lenders and complies with the Truth in Lending Act disclosure standard.