A mortgage is a loan secured by real property. Understanding its components is the first step to making a confident homebuying decision.
Mortgage: The Complete Definition
A mortgage is a loan from a lender (bank, credit union, or mortgage company) that allows you to buy real estate — typically a home — without paying the full purchase price upfront. The home itself serves as collateral. You make monthly payments over a set term (10, 15, 20, or 30 years) until the loan is paid off. If you stop making payments, the lender can foreclose and take ownership of the property.
Every mortgage payment has multiple components. Most homebuyers focus on the principal and interest (P&I) payment — but your true monthly cost is always higher once taxes, insurance, and possibly PMI are included. This calculator shows you the complete picture.
The Four Components of PITI
| Component | What It Is | Paid To | Typical Amount* |
|---|
| Principal | Repayment of the loan balance | Lender (reduces debt) | ~$500–$800/mo |
| Interest | Cost of borrowing money | Lender (their profit) | ~$1,400–$2,000/mo early |
| Taxes | Annual property tax ÷ 12 | Local government via escrow | ~$300–$600/mo |
| Insurance | Homeowners insurance premium ÷ 12 | Insurance company via escrow | ~$100–$200/mo |
| PMI | Private Mortgage Insurance (if <20% down) | Insurance company (protects lender) | ~$100–$300/mo |
*Estimates based on a $400,000 home in 2026. Amounts vary significantly by location, credit score, and lender.
How Amortization Works
Amortization is the process of paying off your loan in equal monthly installments over the loan term. While your payment stays the same every month, the split between principal and interest changes dramatically over time.
$400,000 loan · 7% interest · 30-year term
Month 1 : Payment $2,661 | Interest $2,333 | Principal $328 | Balance $399,672
Month 60: Payment $2,661 | Interest $2,196 | Principal $465 | Balance $375,700
Month 180: Payment $2,661 | Interest $1,808 | Principal $853 | Balance $309,000
Month 300: Payment $2,661 | Interest $972 | Principal $1,689 | Balance $165,000
Month 360: Payment $2,661 | Interest $15 | Principal $2,646 | Balance $0
Total interest paid over 30 years: $558,036
The key insight: In the early years, the vast majority of each payment goes to interest — not paying down your loan. In year 1 of the example above, only $3,936 of $31,932 paid reduces your balance. This is why extra principal payments early in the loan have such a dramatic impact on total interest paid.