About the Mortgage Calculator

What it does

The Computezy Mortgage Calculator estimates your monthly mortgage payment and the total cost of a home loan. Enter a home price, down payment, annual interest rate, and loan term, and the tool instantly applies the standard mortgage amortization formula to return your monthly principal and interest (P&I) payment, total interest paid, and total loan cost. Results update live as you type — no button required.

Monthly payment with taxes, insurance & PMI

The optional section lets you add annual property tax, annual home insurance, monthly PMI (Private Mortgage Insurance), and monthly HOA fees. When any of these are entered, the tool shows a full monthly PITI-style payment — Principal, Interest, Taxes, and Insurance — alongside a breakdown of each component. The amortization schedule and chart always reflect the pure P&I calculation, since taxes and insurance don't affect how your loan balance amortizes.

PMI (Private Mortgage Insurance)

PMI is typically required by lenders when the down payment is less than 20% of the home price (loan-to-value ratio above 80%). It protects the lender rather than the borrower and is usually a monthly cost added to the mortgage payment. Enter your estimated monthly PMI to include it in your full monthly payment total.

Amortization schedule

The tool generates a full payment-by-payment amortization table showing the interest portion, principal portion, and remaining balance for every month of the loan. Each row's interest and principal always sum to the fixed monthly payment. The balance decreases to approximately zero in the final period.

The interest portion of each payment is calculated on the outstanding balance: interest = balance × monthly rate. The principal portion is the payment minus interest. Because the balance is highest at the start, early payments are interest-heavy. As the balance falls, more of each payment goes to principal — this shift is visible in the amortization chart.

Principal vs interest chart

The SVG chart plots principal and interest per payment across the full loan term. The interest area (orange) starts high and falls, while the principal area (green) starts low and rises. The point where they cross is roughly the midpoint where the loan balance has fallen enough that more each payment goes to principal than interest.

International and Indian number formatting

The number system toggle switches all figures between international grouping (e.g. $1,000,000 — millions) and Indian grouping (e.g. ₹10,00,000 — lakhs and crores). Currency symbols switch between $ and ₹ accordingly. Every significant input and output also shows the amount in words beneath the number (e.g. "Four Hundred Thousand" or "Forty Lakhs") as a quick visual check against misplaced zeros.

The maths

Monthly P&I is calculated using the standard fixed-rate mortgage formula:

P = L × r(1 + r)^n / ((1 + r)^n − 1)

Where L is the loan amount (home price minus down payment), r is the monthly interest rate (annual rate ÷ 12 ÷ 100), and n is the total number of monthly payments (years × 12). If the rate is 0%, the payment is simply the loan divided by the number of periods.

Disclaimer

This tool provides general estimates for planning and comparison purposes only. It is not financial advice. Actual mortgage payments, interest rates, fees, property taxes, and insurance premiums vary by lender, loan product, location, and borrower profile. Always confirm all figures with your lender and a qualified financial adviser before making any home purchase or financing decision.