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Mortgage Calculator

Typically 20% to avoid PMI

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How to use the Complete Guide to Mortgage Calculations

A mortgage is a loan used to purchase real estate. Your monthly payment consists of principal (loan amount) and interest. Understanding these calculations helps you make informed home-buying decisions.

🏠 20% Down Payment

Putting 20% down avoids Private Mortgage Insurance (PMI), saving you $100-300/month. It also gives you instant equity in your home.

📅 15 vs 30 Year Term

15-year mortgages have higher payments but save tens of thousands in interest and build equity faster.

The Formula

M = P × [r(1+r)^n] / [(1+r)^n - 1]

Mortgage Term Comparison ($300K Loan @ 6.5%)

Term Monthly Payment Total Interest
15 Years $2,613 $170,340
20 Years $2,238 $237,120
30 Years $1,896 $382,560

Loan Types

  • Fixed-Rate: Interest rate stays the same for the life of the loan (e.g., 30-year fixed). Predictable and safe.
  • ARM (Adjustable-Rate): Rate is fixed for a few years (e.g., 5/1 ARM), then adjusts annually based on market rates. Risky but starts lower.
  • FHA/VA Loans: Government-backed loans with lower down payment requirements, ideal for first-time buyers or veterans.

Hidden Costs of Ownership

  • Escrow Accounts: Lenders often collect 1/12th of your annual Tax and Insurance bills each month, holding them in an "Escrow" account to pay on your behalf.
  • HOA Fees: Homeowners Association fees are paid separately and can range from $50 to $1000+ per month.
  • Maintenance: Rule of thumb: Budget 1% of your home's value annually for repairs (e.g., $3,000/year for a $300k home).

Frequently Asked Questions

What is PMI and how do I avoid it?

Private Mortgage Insurance (PMI) is required when you put less than 20% down. It protects the lender if you default. Avoid it by putting 20% down or using a piggyback loan (80-10-10).

How much house can I afford?

The general rule: your monthly payment (including taxes & insurance) shouldn't exceed 28% of gross income. Total debt payments shouldn't exceed 36% of income.

Should I pay points to lower my rate?

Each "point" costs 1% of loan amount and typically lowers rate by 0.25%. It's worth it if you plan to stay in the home long enough to break even (usually 4-7 years).