🏠 Mortgage Calculator
What this mortgage calculator does
Enter a home price, a down payment, a loan term, an interest rate and your yearly property tax and home insurance. The calculator returns the monthly principal-and-interest payment, the full monthly payment including tax and insurance, the loan amount, the total interest over the life of the loan, and a year-by-year table showing how much of each year's payments goes to principal and how much to interest. The sums run in your browser and nothing you type is sent anywhere.
The formula
For a fixed-rate loan, the monthly payment is M = L × r × (1 + r)n ÷ ((1 + r)n − 1), where L is the loan amount (price minus down payment), r is the monthly rate (annual rate ÷ 12) and n is the number of monthly payments (years × 12). If the rate is 0%, the payment is simply L ÷ n. Property tax and insurance are added on top as one-twelfth of the yearly amounts.
Worked example
A $350,000 home with $70,000 down (20%) leaves a loan of $280,000. At 6.8% over 30 years:
- Monthly principal and interest: $1,825.39.
- With $3,600 a year in property tax and $1,200 a year in insurance (another $400 a month), the full monthly payment is $2,225.39.
- Total paid over 30 years on the loan itself: $657,140.59, so total interest is $377,140.59, more than the amount borrowed.
- In month one, $1,586.67 of the payment is interest and only $238.72 reduces the loan. After five years the balance is still $262,997.25, so only about $17,000 of the $280,000 has been repaid.
Same loan, different term or rate
- 15 years instead of 30 (still 6.8%): the payment rises to $2,485.51 but total interest falls to $167,392.69, a saving of about $209,700.
- 6.0% instead of 6.8% (30 years): the payment is $1,678.74, which is $146.65 a month less and about $52,800 less interest over the loan.
This is why early payments feel like they barely move the balance. Interest is charged on what you still owe, so it is front-loaded.
What the result leaves out
- Mortgage insurance. In the US, lenders usually require private mortgage insurance on conventional loans when the down payment is below 20%. It is not included here, so add it to the monthly figure if it applies.
- HOA fees, closing costs and maintenance. None are included.
- Rate changes. The calculator assumes one fixed rate for the whole term. Many lenders, including many in the UAE, fix the rate for an initial period and then move to a variable rate, so the result only describes the fixed period. Ask for the rate after the fixed period.
- Currency. The labels show dollars, but the arithmetic works for any currency. Just enter amounts in the same currency throughout.
- Total Cost. The "Total Cost" figure is principal, interest and down payment. It does not include tax and insurance.
How to use it for a decision
Work backwards from what you can pay each month, not from the price. Try a larger down payment, a shorter term and a slightly higher rate and compare the monthly payment with the total interest in each case. A traditional guideline, the "28/36 rule", suggests keeping the housing payment under about 28% of gross income and total debt payments under about 36%, but it is only a guideline, and your other debts and savings matter more than any ratio. Ask lenders for a written estimate, because the real rate depends on your credit, the loan type and the day you lock it.
This tool gives estimates only. It is not financial advice, so talk to a licensed mortgage professional before you commit.
Sources
The payment formula is the standard fixed-rate amortisation formula. Mortgage insurance: US Consumer Financial Protection Bureau, "What is private mortgage insurance?"