How Does a Mortgage Work? (2026)
A mortgage is a loan you use to buy a home, secured by the home itself, that you repay in monthly installments of principal and interest over a set term, usually 15 or 30 years. Because the home is the collateral, the lender can foreclose if you stop paying. Understanding the four parts of the payment and how amortization works makes the whole thing much less mysterious.
What makes up your monthly payment: PITI
Your monthly mortgage payment usually bundles four things, remembered as PITI:
| Part | What it is |
|---|---|
| Principal | Pays down the amount you borrowed |
| Interest | The lender’s charge for the loan |
| Taxes | Property taxes, collected into escrow |
| Insurance | Homeowners insurance (and PMI if under 20% down), via escrow |
The lender holds the tax and insurance portions in an escrow account and pays those bills for you when they come due.
Amortization: why early payments are mostly interest
Mortgages are amortized, meaning each payment is the same, but the split between principal and interest shifts over time. Early on, most of your payment goes to interest; near the end, most goes to principal. That is why making extra principal payments early saves so much interest, and why you build equity slowly at first.
Fixed vs. adjustable rate
- Fixed-rate mortgage: the interest rate never changes, so your principal-and-interest payment stays the same for the whole term. Predictable and the most common choice.
- Adjustable-rate mortgage (ARM): the rate is fixed for an intro period (say 5 or 7 years), then adjusts periodically with the market. Lower at first, but the payment can rise later.
The other pieces
- Down payment: your upfront share. Less than 20% usually means paying PMI.
- Term: 30 years means lower payments but more total interest; 15 years means higher payments but far less interest overall.
- What if you stop paying: after missed payments, the lender can begin foreclosure and take the home, which is why a mortgage is a serious long-term commitment.
Bottom line
- A mortgage is a home-secured loan repaid as principal + interest over 15 or 30 years.
- Your payment is PITI: principal, interest, taxes, and insurance.
- Amortization front-loads interest, and you choose between a steady fixed rate or a lower-then-variable ARM.
See exactly how your payment breaks down, and how extra payments help, with our mortgage calculator and mortgage payoff calculator. This article is general information, not financial advice.
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Rakesh Choudhary, PhD · Founder & Editor
Rakesh Choudhary, PhD, is the founder of Calcinum. A sociologist by training, he builds every calculator on the site and maintains its 2026 federal and state tax data, sourced from primary references (IRS, SSA, state revenue departments, DFAS) and re-verified whenever the law changes. Tax data is sourced from primary references (IRS, state revenue departments, SSA, DFAS) and re-verified annually each tax year.
Editorial standards: Every article cites primary sources and is reviewed against current tax-law data before publication. See our full methodology & accuracy for sourcing and review process.
Not financial advice: This article is for general informational purposes only. Calcinum does not provide regulated tax, legal, or investment advice. Consult a qualified professional for decisions specific to your situation.