30-Year Mortgage Calculator

Worked example

Example: $450,000 home with $90,000 down (20%), 6.75% rate, and a 30-year term gives roughly $2,334/month principal and interest on a $360,000 loan—about $480,000 in total payments over 30 years.

When to use this

• Estimating payments on a standard 30-year fixed offer.
• Comparing a 30-year payment to rent for a buy-vs-rent decision.
• Checking how rate changes affect a 30-year installment.
• Modeling a first home purchase with 20% down.

Common examples

• Buying a $350,000 home with 20% down ($70,000), 6.5% APR, 30 years, $4,200/year tax and $1,800/year insurance → principal and interest near $1,770/month; total housing payment near $2,270/month before PMI.
• Buying a $500,000 home with 10% down ($50,000), 7% APR, 30 years, $6,000/year tax, $2,400/year insurance, and $150/month HOA → P&I near $2,994/month; estimated total near $3,844/month.
• First-time buyer: $275,000 home with 5% down ($13,750), 6.75% APR, 30 years, modest tax and insurance → P&I near $1,694/month; total near $2,094/month—PMI often applies below 20% down.
• $425,000 home with 15% down, 6.75% APR, 30 years → P&I near $2,350/month before tax and insurance.
• Refinance scenario: $280,000 remaining balance at 5.9% for 25 years → compare to current 6.5% payment on the same balance.

Common mistakes

• Comparing a 30-year payment to a 15-year quote without noting total interest.
• Assuming the rate is locked without confirming with the lender.
• Using list price instead of the financed amount after down payment.
• Ignoring that ARM products are not 30-year fixed loans.

How it works

Enter the home price, down payment ($ or % of home price), interest rate, and term. The calculator derives the loan amount and uses the standard amortizing loan formula for principal and interest. Optional annual property tax ($/yr or % of home), home insurance, monthly HOA, and PMI (when LTV is above 80%) are added to estimate a total monthly payment.

Limitations

Monthly payment estimates exclude HOA, PMI changes, escrow adjustments, and property tax reassessments. Not a loan offer or pre-approval.

Privacy and file handling

Your data stays on your device and is not uploaded.

Accuracy & methodology

This section documents how the calculator works, what it leaves out, and when results were last reviewed. Figures are educational estimates—not professional advice—and are not labeled "current" unless tied to automatically updated reference data.

Formula source or methodology

Loan amount = home price − down payment. Monthly principal & interest uses the standard amortizing loan payment formula (same as loan calculator). Optional annual property tax, insurance, and HOA are divided by 12 and added to P&I for total monthly housing payment.

Jurisdiction

General mortgage math (not country-specific underwriting rules)

Unit system

Currency for price, down payment, tax, insurance, HOA; years for term; percent for rate

Rounding method

Currency amounts round to two decimal places (half up via Math.round × 100 / 100).

Assumptions

• Fixed annual interest rate for the full term
• Level monthly payments (fully amortizing)
• Down payment is a dollar amount, not a separate percent field

Known omissions

• Not tax, legal, investment, or lending advice. Confirm material decisions with qualified professionals.
• Origination fees, points, PMI/MIP, and lender-specific charges unless a field exists
• Property taxes, insurance, and HOA unless explicitly entered
• Prepayment penalties and variable or adjustable rates after the initial period
• Tax deductibility of interest

Test cases (automated)

• Typical home price, down payment, rate, and term return positive P&I and total interest
• Down payment greater than home price is rejected

Version & last verified

Logic version 1.0. Content and formulas last verified 2026-07-24.

Important notice

Results are estimates for educational purposes and are not financial advice. Taxes, insurance, HOA fees, and lender-specific costs may not be included. Consult a qualified financial professional for personal guidance.