Estimate Your Monthly Mortgage Payment
Understanding Your Mortgage Calculation
Purchasing a home is likely the largest financial decision you will make in your lifetime. Understanding how your monthly mortgage payment is calculated is essential for budgeting and ensuring long-term financial stability. Our Mortgage Payment Calculator breaks down the costs so you can see exactly where your money goes every month.
The 4 Pillars of a Mortgage Payment (PITI)
Most mortgage payments are comprised of four distinct parts, often referred to by the acronym PITI:
- Principal: The portion of your payment that goes toward paying down the original amount you borrowed. In the early years of a loan, this amount is small but grows over time.
- Interest: The cost of borrowing money from your lender. This is calculated based on your annual interest rate and remaining loan balance.
- Taxes: Property taxes charged by your local government. These are usually held in an escrow account by your lender and paid annually on your behalf.
- Insurance: Homeowners insurance protects your property against damage. Like taxes, this is typically paid monthly into an escrow account.
How the Math Works
While taxes and insurance are simple divisions (Annual Cost / 12), calculating the Principal and Interest (P&I) requires a standard amortization formula:
M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
Where:
- M = Total monthly P&I payment
- P = The principal loan amount (Home Price minus Down Payment)
- i = Monthly interest rate (Annual Rate / 100 / 12)
- n = Number of months in the loan term (Years × 12)
For example, if you buy a home for $350,000 with a $70,000 down payment (leaving a $280,000 loan amount) at a 6.5% interest rate for 30 years, the formula ensures that by the end of the 360th month, your balance is exactly zero.
Impact of Interest Rates and Down Payments
Even a small change in your interest rate can have a massive impact on your monthly obligation. For a $300,000 loan, the difference between a 6% and a 7% interest rate is roughly $199 per month. Over the life of a 30-year loan, that adds up to over $71,000 in extra interest.
Similarly, increasing your down payment reduces your Principal (P), which not only lowers your monthly payment but also reduces the total interest paid. If you put down less than 20%, you may also be required to pay Private Mortgage Insurance (PMI), which would be an additional cost on top of the calculated total above.