Monthly mortgage payment is calculated using the standard amortization formula: M = P[r(1+r)^n] / [(1+r)^n - 1], where P is the principal loan amount, r is the monthly interest rate (annual rate divided by 12), and n is the total number of monthly payments. For example, a $250,000 loan at 5.5% for 30 years gives a monthly payment of approximately $1,419. This formula ensures each payment covers interest on the remaining balance plus a portion of principal, so the loan is fully paid off by the end of the term.
An amortization schedule (also called an amortization table) is a complete month-by-month breakdown of every payment over the life of your loan. Each row shows the payment number, date, total payment amount, how much goes toward principal, how much goes toward interest, any extra payments, and the remaining balance. In the early years, most of your payment goes to interest. As the balance decreases, more goes to principal. This calculator generates a full interactive amortization schedule that you can scroll through, export as CSV, or print.
The standard guideline is the 28% DTI (debt-to-income) rule: your monthly housing payment should not exceed 28% of your gross monthly income. For example, if you earn $6,000/month gross, your maximum mortgage payment should be $1,680. Use the Affordability tab in this calculator to enter your income, existing debts, down payment, interest rate, and term to get your maximum affordable loan amount. Keep in mind that lenders also look at your total DTI (all debts combined), which should ideally stay below 36%.
Extra payments go directly toward reducing your principal balance. Since interest is calculated on the remaining balance each month, a lower balance means less interest accrues. This creates a compounding effect: each extra payment saves more than just its face value. For example, adding just $200/month in extra payments to a $300,000, 30-year mortgage at 6% can save you over $80,000 in interest and pay off the loan 7 years early. Enter an extra payment amount in the calculator to see your exact savings.
A 15-year mortgage typically has a lower interest rate and saves a massive amount on total interest, but comes with significantly higher monthly payments. A 30-year mortgage offers lower monthly payments and more flexibility, but costs much more in total interest. For example, on a $300,000 loan: a 15-year at 5% costs ~$2,372/month with ~$127,000 total interest, while a 30-year at 5.5% costs ~$1,703/month but ~$313,000 total interest. Use the Compare tab to see the exact numbers for your situation side-by-side.
DTI (debt-to-income) ratio is the percentage of your gross monthly income that goes toward debt payments. There are two types: front-end DTI (housing costs only, target under 28%) and back-end DTI (all debts including car loans, student loans, credit cards, target under 36%). Lenders use DTI to assess whether you can comfortably afford a mortgage. A lower DTI means you are a lower risk borrower and more likely to be approved at favorable rates.
Total interest is calculated as: Total Interest = (Monthly Payment x Number of Payments) - Loan Amount. For example, if your monthly payment is $1,419 on a $250,000 loan with 360 payments (30 years), total interest = ($1,419 x 360) - $250,000 = $260,840. This calculator shows total interest automatically, and the amortization table breaks down exactly how much interest you pay each month.
Yes. Making biweekly payments (every two weeks) instead of monthly payments results in 26 half-payments per year, which equals 13 full monthly payments instead of 12. That extra payment each year goes directly to principal, which can shave years off your mortgage and save thousands in interest. The effect is similar to making one extra monthly payment per year. You can simulate this in the calculator by entering your extra monthly equivalent (monthly payment divided by 12) in the extra payment field.
The interest rate is the cost of borrowing the principal amount, expressed as a percentage. The APR (Annual Percentage Rate) includes the interest rate plus other costs like origination fees, closing costs, mortgage insurance, and discount points, making it a more complete picture of the loan's total cost. APR is always equal to or higher than the interest rate. When comparing loans from different lenders, APR is more useful because it accounts for all fees. This calculator uses the nominal interest rate for payment calculations.
With a $100,000 annual salary ($8,333/month gross), using the 28% DTI rule, your maximum monthly housing payment would be about $2,333. At a 6% interest rate with a 30-year term, this supports a loan of approximately $389,000. With a 20% down payment of $97,000, you could afford a home priced around $486,000. These numbers vary based on your existing debts, credit score, interest rate, and location. Use the Affordability tab to calculate your specific situation.
Yes, completely free. No account, no subscription, no watermark, no ads. All calculations run locally in your browser and your financial data never leaves your device. It is one of the free browser-based tools at jasperbernaers.com.
Absolutely. While often called a mortgage calculator, this tool works for any fixed-rate or adjustable-rate amortized loan including car loans, personal loans, student loans, and business loans. Simply enter the loan amount, interest rate, and term. The amortization formula is the same regardless of loan type. You can also use the extra payment feature to see how additional payments reduce your car loan or personal loan payoff time.