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Mortgage Calculator

Estimate your monthly PITI payment instantly. No sign-up, no upload, works offline.

How Mortgage Calculator works

The mortgage calculator estimates your monthly payment broken into four components: principal and interest computed with the standard annuity formula M = L * r / (1 - (1 + r)^-n), property tax, homeowner insurance and PMI. Enter home price, down payment, annual rate and loan term to see the full monthly obligation at a glance. All figures are computed in your browser; nothing you enter is sent to any server.

The optional costs section lets you model the true monthly obligation rather than just the bare loan payment. PMI is typically required when the down payment falls below 20 percent of the home price, usually in the range of 0.2 to 1.5 percent of the loan per year. Toggle between a 15-year and a 30-year term to compare total interest paid over the life of the loan, or stress-test a rate increase to see how sensitive your budget is. This tool provides estimates for orientation only and is not a substitute for advice from a licensed lender.

Written by Bastien Sulyan

How to use Mortgage Calculator, step by step

  1. Enter the home price and the down payment amount.
  2. Set the annual interest rate and the loan term in years.
  3. Optionally add monthly property tax, homeowner insurance and annual PMI rate.
  4. Read the monthly payment breakdown: principal and interest, tax, insurance, PMI and total.
  5. Adjust any value to model different scenarios, such as a shorter term or a higher down payment.

Common use cases

  • A first-time buyer compares a 15-year and a 30-year mortgage on the same home to weigh lower monthly cost against total interest paid.
  • A couple stress-tests their budget by raising the rate by 1.5 percentage points to check affordability if rates climb.
  • A renter deciding whether to buy estimates the true monthly cost by adding property tax and insurance to the loan payment.
  • An investor evaluates whether rental income will cover the full monthly mortgage obligation including PMI on a low-down-payment purchase.

Frequently asked questions

Does the mortgage calculator transmit the figures I enter to a server?

No. Every calculation runs in your browser tab using standard JavaScript arithmetic. The home price, down payment, rate, term and all optional figures stay on your device. The tool works offline once the page has loaded.

How is the principal-and-interest payment calculated?

The tool uses the standard annuity formula: M = L * r / (1 - (1 + r)^-n), where L is the loan amount (home price minus down payment), r is the monthly interest rate (annual rate divided by 12) and n is the number of payments. If the rate is zero the formula simplifies to L / n.

When should I include PMI in my estimate?

Private Mortgage Insurance is typically required by US lenders when the down payment is less than 20 percent of the home price. A common range is 0.2 to 1.5 percent of the loan amount per year, billed monthly. Leave the PMI field blank if your down payment is 20 percent or more.

Is the monthly payment estimate accurate enough to use in a real purchase decision?

The principal-and-interest figure is mathematically exact for a fixed-rate fully amortizing loan. Property tax and insurance depend entirely on your inputs. The total is a solid starting point, but always confirm with a licensed mortgage lender who can account for local taxes, escrow requirements and your credit profile.

Can I model an adjustable-rate mortgage (ARM)?

This tool is designed for fixed-rate loans. For an ARM you can enter the initial fixed rate to see the payment during the introductory period, then re-run with the expected adjusted rate to see what the payment could become. It does not model rate caps or adjustment schedules automatically.

What is the difference between a 15-year and a 30-year term in practice?

A 30-year term gives a lower monthly payment but results in significantly more total interest paid over the life of the loan. A 15-year term has a higher monthly payment but you build equity faster and pay far less interest overall. Enter both scenarios and compare the Total Interest field to see the difference in concrete dollar terms.

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