How to Calculate a Mortgage Payment (PITI Explained)

Most first-time buyers make the same mistake: they shop for a home based on a principal-and-interest payment and then get a nasty surprise when the real monthly bill arrives. The reason is that a mortgage isn't just a loan — it's a package. In most markets the lender collects property tax and insurance along with your monthly payment and holds them in an escrow account, disbursing them when due. Lenders and sellers call the whole thing PITI: Principal, Interest, Taxes, and Insurance. Here's how to estimate the full payment before you fall for a listing.

Step 1 — Principal & interest

The loan portion uses the standard amortization formula:

Monthly P&I = P × r × (1 + r)ⁿ / ((1 + r)ⁿ − 1)

Where:

• P = home price − down payment (the actual loan amount)
• r = monthly interest rate = annual rate ÷ 12 ÷ 100
• n = number of months = years × 12

Step 2 — Add taxes and insurance

These are spread over 12 months:

• Property tax: annual tax (typically a percentage of the assessed value) ÷ 12
• Home insurance: annual premium ÷ 12

Step 3 — Add PMI if your down payment is under 20%

Lenders require private mortgage insurance when your down payment is below 20% — it protects the lender if you default. It typically runs 0.5–1.5% of the loan per year, divided by 12 and added to the payment. The good news: PMI drops off automatically once you reach 20% equity, which is a strong argument for building equity faster.

Worked example

A $350,000 home with $70,000 down (20%) at 6.5% for 30 years:

P = $350,000 − $70,000 = $280,000
r = 0.065 ÷ 12 = 0.00542
n = 30 × 12 = 360

P&I = $280,000 × 0.00542 × (1.00542)³⁶⁰ / ((1.00542)³⁶⁰ − 1) ≈ $1,770

Property tax   ($3,000/yr)  = $250/month
Home insurance ($1,200/yr)  = $100/month
20% down → no PMI

Total monthly payment (PITI) ≈ $2,120

Now here's the reveal that surprises people: over 30 years that $2,120 monthly payment includes roughly $357,000 of interest — more than the original loan. The PITI number is what you pay every month; the total-interest number is what the loan actually costs.

The 28% rule

Lenders generally cap your total housing payment (PITI) at about 28% of gross monthly income. For the $2,120 payment above, you'd want roughly $7,570/month gross — about $90,000 a year. This is a front-end ratio; combined with your other debts, most lenders also watch that your total obligations stay under about 36% of income.

The 15-year alternative

Choosing a 15-year term instead of 30 changes the picture dramatically:

Term	P&I payment	Total interest
30 years	$1,770	~$357,000
15 years	~$2,440	~$160,000

Your monthly payment jumps by roughly $670, but you shave ~$197,000 of interest and own the home outright in half the time. It's the single biggest lever a serious buyer can pull.

Common mistakes

1. Quoting only the P&I — always add tax and insurance; the "real" payment is often 25–40% higher.
2. Forgetting PMI — a 10% down payment sneaks PMI into the bill for years until you cross 20% equity.
3. Ignoring closing costs — not part of PITI, but a real upfront expense that factors into affordability.

Key takeaways

• A mortgage payment = PITI: principal, interest, taxes, insurance — plus PMI below 20% down.
• The monthly amount and the total-interest amount are two different questions; don't conflate them.
• The 28% rule is a useful affordability check, not a guarantee of approval.
• A 15-year term costs far less in interest for buyers who can carry the higher payment.

Work out your exact figures with the Mortgage Payment Calculator, check how your overall obligations look with the Debt-to-Income Calculator, or compare with a Loan EMI Calculator for an equivalent Indian home-loan view.

FAQ

What does PITI stand for?

Principal, Interest, Taxes, and Insurance — the four components of a mortgage payment. Principal and interest repay the loan; taxes and insurance are collected in escrow and paid on your behalf.

Why do I need PMI, and when does it go away?

Lenders require private mortgage insurance when your down payment is under 20% to protect against default. It's removed automatically once your equity reaches 20% — either through payments or appreciation.

Should I pay off my mortgage early?

It depends on your interest rate versus what your money could earn elsewhere. If your mortgage is at a high rate, prepaying gives a guaranteed return equal to that rate. At a low rate, the same cash might do better in the market — and you shouldn't neglect higher-interest debts first.