Mortgage Payment Calculator

How to Calculate Your Mortgage Payment

A mortgage payment calculator takes four inputs — home price, down payment, interest rate, and loan term — and returns your exact monthly payment. The math behind it is a standard amortization formula:

M = P × [r(1+r)ⁿ] / [(1+r)ⁿ – 1]

Where M is your monthly payment, P is the principal (loan amount), r is the monthly interest rate (annual rate ÷ 12), and n is the total number of payments (years × 12). If that looks intimidating, don't worry — the calculator handles it instantly.

A Real-World Example

Let's say you're buying a $400,000 home with a $80,000 down payment (20%), a 6.75% annual interest rate, and a 30-year term.

• Loan amount: $320,000
• Monthly interest rate: 6.75% ÷ 12 = 0.5625%
• Number of payments: 30 × 12 = 360
• Monthly payment: approximately $2,076
• Total paid over 30 years: approximately $747,360
• Total interest: approximately $427,360

That interest figure surprises most people. Over 30 years, you'd pay more in interest than you borrowed. That's why many financial advisors recommend putting more down or choosing a shorter term when your budget allows.

How Loan Term Affects Your Payment

Using the same $320,000 loan at 6.75%, here's how the term changes everything:

• 10-year term: $3,673/month — but only $120,760 total interest
• 15-year term: $2,834/month — $190,200 total interest
• 20-year term: $2,424/month — $261,760 total interest
• 30-year term: $2,076/month — $427,360 total interest

The 10-year loan costs $1,597 more per month than the 30-year — but saves over $306,000 in interest. The right choice depends on your cash flow, other debts, and investment goals.

Down Payment: How Much Is Enough?

The minimum down payment depends on your loan type. Conventional loans allow as little as 3%, FHA loans require 3.5% (with a 580+ credit score), and VA or USDA loans may require nothing down. But the amount you put down has a direct impact on your payment, your equity, and whether you owe PMI.

On a $400,000 home, the difference between 5% down ($20,000) and 20% down ($80,000) is significant:

• 5% down → $380,000 loan → roughly $2,469/month P&I + PMI
• 20% down → $320,000 loan → roughly $2,076/month P&I, no PMI

The larger down payment lowers your balance, eliminates PMI, and reduces the total interest you'll pay over the life of the loan.

Understanding Your Amortization Schedule

Every mortgage payment includes two parts: principal (which reduces your balance) and interest (the lender's fee for the loan). At the start of a 30-year mortgage, roughly 80% of each payment goes to interest. By the final years, nearly all of it goes to principal.

This front-loading of interest is why paying extra principal early in the loan has such a large impact. An extra $200/month on a $320,000, 30-year, 6.75% mortgage could cut about 5–6 years off the loan and save tens of thousands in interest.

What's Not Included in This Calculator

This tool calculates principal and interest only. Your full monthly housing cost includes additional items your lender typically collects into an escrow account:

• Property taxes: Varies widely by state and county — typically 0.5% to 2.5% of home value per year
• Homeowner's insurance: Usually $100–$200/month for a standard policy
• PMI (if applicable): 0.5–1.5% of loan amount annually, required if down payment is under 20% on conventional loans
• HOA fees: If you're buying in a homeowners association, add this monthly fee too

Add these to the P&I figure from this calculator to estimate your true all-in monthly housing cost.

Tips for Getting a Better Mortgage Rate

Your interest rate is the most powerful lever you have on your total mortgage cost. Even a 0.5% difference in rate on a $350,000 loan saves over $35,000 in interest over 30 years. Here's how to get the best rate:

• Check your credit score before applying — 760+ typically gets the best rates
• Reduce your debt-to-income ratio by paying down existing debts
• Shop at least 3–5 lenders, including banks, credit unions, and mortgage brokers
• Consider buying points to lower your rate if you plan to stay in the home long-term
• Get pre-approved before house hunting — it shows sellers you're serious

Fixed vs. Adjustable Rate Mortgages

This calculator assumes a fixed-rate mortgage, where the interest rate stays the same for the entire loan term. That's what most buyers choose, because the payment is predictable. Adjustable-rate mortgages (ARMs) start with a lower fixed rate for 3, 5, 7, or 10 years, then adjust annually based on a market index.

ARMs can be a smart choice if you plan to sell or refinance before the adjustment period — but carry risk if rates rise significantly. Always calculate the worst-case scenario with an ARM before committing.