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Mortgage Rate Calculator

Calculate your full monthly mortgage payment including principal, interest, property taxes, and insurance using your home price, rate, and loan term.

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How the Mortgage Rate Calculator Works

A monthly mortgage payment combines two core components: the amortized principal-and-interest payment and the monthly escrow costs for property taxes and homeowner's insurance. The mortgage rate calculator applies a standard actuarial formula to compute the full monthly obligation, helping borrowers evaluate affordability before committing to a purchase.

The Core Formula

The fixed-rate mortgage payment formula is:

M = P · [r(1+r)n] / [(1+r)n − 1] + (T + I) / 12

Each variable in the formula represents a specific financial input:

  • M — Total monthly mortgage payment
  • P — Principal loan amount (home price minus down payment)
  • r — Monthly interest rate (annual rate ÷ 12)
  • n — Total number of monthly payments (loan term in years × 12)
  • T — Annual property tax based on the home value and state rate
  • I — Annual homeowner's insurance premium

Understanding Loan Amortization

The expression P · r(1+r)n / [(1+r)n − 1] is the amortization factor. Amortization distributes equal payments across the loan's life so that early payments cover mostly interest, while later payments pay down more principal. On a 30-year loan at 7% APR, approximately 77% of the very first payment goes toward interest. By year 25, that ratio reverses substantially, with principal comprising the majority of each payment. This structure benefits lenders and makes early payoff strategies particularly valuable for reducing total interest costs.

How Property Taxes Are Applied

Property tax rates differ significantly across states and counties. This calculator applies state-specific effective property tax rates sourced from the Tax Foundation to the home's purchase price, then divides by 12 to produce the monthly escrow contribution. For example, New Jersey's effective rate of 2.23% on a $400,000 home adds $743 per month to the payment, while Hawaii's 0.32% rate adds only $107 per month—a difference of $636 monthly, or $7,632 annually, from taxes alone.

Step-by-Step Calculation Example

Consider a $450,000 home with a $90,000 down payment (20%), a 6.75% annual interest rate, a 30-year term, and a Texas location (effective property tax rate: 1.68%):

  • Principal (P): $450,000 − $90,000 = $360,000
  • Monthly rate (r): 6.75% ÷ 12 = 0.5625% = 0.005625
  • Number of payments (n): 30 × 12 = 360
  • Amortized payment: $360,000 × [0.005625 × (1.005625)360] / [(1.005625)360 − 1] ≈ $2,335/month
  • Annual property tax (T): $450,000 × 1.68% = $7,560 → $630/month
  • Annual insurance (I): ~$1,200 → $100/month
  • Total monthly payment (M): $2,335 + $630 + $100 = $3,065

The Role of the Down Payment

A larger down payment directly reduces the principal balance (P), lowering the amortized portion of the monthly payment. Borrowers who put down less than 20% typically owe private mortgage insurance (PMI), which adds 0.5%–1.5% of the loan amount annually. As the Consumer Financial Protection Bureau explains, selecting the right loan structure—including down payment size and loan type—can save tens of thousands of dollars over the life of a mortgage.

Fixed vs. Adjustable Rates

This calculator uses a fixed annual interest rate, meaning the amortized payment remains constant for the entire loan term. Adjustable-rate mortgages (ARMs) offer a fixed rate for an initial period—commonly 5 or 7 years—then reset annually based on market indexes. Fixed-rate loans deliver payment predictability; ARM loans may start lower but carry rate-reset risk over time.

Applying the 28/36 Affordability Rule

Lenders commonly apply the 28/36 rule: housing costs should not exceed 28% of gross monthly income, and total debt should stay below 36%. On a $100,000 annual salary (~$8,333/month), a safe housing budget is approximately $2,333 per month. According to FDIC Consumer News, understanding the complete cost of homeownership—including taxes, insurance, and ongoing maintenance—is essential before committing to any purchase decision.

Reference

Frequently asked questions

What is a good mortgage interest rate in 2025?
A competitive mortgage rate in 2025 depends on credit score, loan type, and market conditions. Rates for a 30-year fixed mortgage have ranged from approximately 6.5% to 7.5% for well-qualified borrowers with credit scores above 740. Borrowers with scores below 680 typically receive rates 0.5 to 1.5 percentage points higher, adding tens of thousands of dollars in total interest over the loan's life. Shopping at least three lenders can reduce the rate by 0.25% to 0.5%.
How does the down payment amount affect my monthly mortgage payment?
A larger down payment reduces the loan principal directly, lowering the amortized monthly payment. On a $400,000 home at 7% interest over 30 years, a 10% down payment ($40,000) produces a principal of $360,000 and a payment of roughly $2,395, while a 20% down payment ($80,000) reduces principal to $320,000 and the payment to about $2,129. Reaching 20% also eliminates private mortgage insurance (PMI), saving an additional $100 to $400 per month depending on the lender.
What costs are included in a total monthly mortgage payment?
A complete monthly mortgage payment typically covers four components known as PITI: Principal (reduction of loan balance), Interest (cost of borrowing), Taxes (monthly property tax escrow), and Insurance (homeowner's insurance escrow). Private mortgage insurance (PMI) applies when the down payment is below 20%. This calculator includes principal, interest, a state-specific property tax based on the home's purchase price, and a baseline insurance estimate to reflect the true all-in monthly cost.
How does loan term length affect the total interest paid on a mortgage?
Loan term length dramatically affects the total interest paid over the life of a mortgage. On a $300,000 loan at 7% interest, a 30-year term produces a monthly payment of about $1,996 but accumulates approximately $418,560 in total interest. The same loan on a 15-year term raises the monthly payment to roughly $2,696 but reduces total interest to about $185,280—a lifetime savings of over $233,000. Shorter terms carry higher monthly payments but substantially lower total borrowing costs.
What is the difference between a mortgage interest rate and APR?
The mortgage interest rate is the annual cost of borrowing the principal, expressed as a percentage and used to calculate monthly payments. The Annual Percentage Rate (APR) incorporates the interest rate plus lender fees, origination charges, discount points, and other closing costs, making it a broader measure of total borrowing expense. APR is almost always higher than the stated rate. When comparing competing loan offers, use the APR figure to make an accurate apples-to-apples comparison of true cost.
How do state property taxes affect my total monthly mortgage payment?
State property tax rates vary widely and significantly affect monthly escrow costs. According to the Tax Foundation, effective state rates range from Hawaii's 0.32% to New Jersey's 2.23%. On a $400,000 home, that gap translates to an annual property tax of $1,280 versus $8,920—a monthly escrow difference of $636. Choosing a home in a lower-tax state or county can reduce the monthly payment substantially without changing the loan terms. This calculator automatically applies the state-specific effective rate to the home value.