Mortgage Calculator

What this calculator does

This calculator turns a purchase scenario into a loan balance, principal-and-interest payment, estimated monthly total, and total interest. It is designed to make the difference between the advertised home price and the ongoing cash commitment visible before you compare listings or lender offers.

When to use it

Use it before a viewing, after receiving a rate estimate, or when comparing a larger down payment with a lower monthly payment. It is also useful for a sensitivity check: keep the home and term the same, then test a higher rate or a more realistic insurance and property-tax assumption.

Inputs explained

• Home price: the agreed or target purchase price before subtracting cash paid upfront.
• Down payment: cash paid at closing that reduces the amount borrowed; it does not include every closing cost.
• Interest rate: the annual fixed rate used to model principal and interest, not necessarily the APR or a lender commitment.
• Loan term: the scheduled repayment length. A longer term normally lowers the payment but can raise total interest.
• Property tax: the yearly tax estimate divided by 12 for budgeting. Local assessments and escrow can change it.
• Home insurance: the yearly premium divided by 12. Coverage, claims history, location, and insurer can change it.

Formula or method

The model starts with home price minus down payment. It converts the annual rate to a monthly rate and uses the standard fixed-payment amortization formula to calculate principal and interest. Annual property tax and insurance are divided by 12 and added afterward, so they do not change the modeled loan balance or interest.

Worked example

For a $400,000 home with $80,000 down, the starting loan balance is $320,000. At 6.5% over 30 years, principal and interest are about $2,023 per month. Entering $4,800 for annual tax and $1,800 for annual insurance adds $550 per month, taking the modeled housing cash flow to roughly $2,573 before HOA dues, mortgage insurance, utilities, maintenance, and closing costs.

How to interpret the result

Read the principal-and-interest line as the cost of financing the borrowed balance. Read the estimated monthly total as a planning number, not a guarantee: it deliberately excludes costs that you did not enter and it does not establish eligibility or a rate lock.

Practical checks before using the result

• Run one version with the quoted rate and another one percentage point higher. The difference shows how much rate uncertainty can move the monthly payment before a lender issues a final offer.
• Keep closing costs, mortgage insurance, HOA dues, repairs, utilities, and moving costs in a separate comparison. Folding them into a single payment can hide what is recurring and what is one-time.
• Compare the payment with stable monthly take-home income, not only gross salary. A housing budget can be stressed even when a lender's qualifying model allows the loan.

Common mistakes

• Treating the interest rate as the APR. APR can include certain lender charges, while this payment formula uses the stated rate only.
• Using a property-tax amount from another neighborhood or an old assessment. Taxes and insurance can be material parts of monthly housing cost.
• Assuming a 20% down payment eliminates every extra charge. Mortgage insurance, fees, and lender conditions depend on the actual product and borrower profile.

Limitations and disclaimers

These results are general estimates only and are not financial, tax, or legal advice. They are not a mortgage quote, a lending decision, or a closing disclosure. Actual cost can vary with lender pricing, fees, points, mortgage insurance, escrow practices, local taxes, insurance, HOA dues, credit profile, and product terms.

Related calculator context

After estimating a monthly payment, use the Amortization Calculator to inspect how early payments split between interest and principal. The Rent vs Buy Calculator is useful when the next question is whether the monthly cash commitment fits better than a current rental budget.