Free Online Mortgage Calculator
Understanding your mortgage payment before you commit is one of the most important steps in home buying. A home is often the largest purchase you will ever make, and even a small difference in interest rate or down payment can change your monthly budget by hundreds of dollars. Our free mortgage calculator uses the standard amortization formula to show your exact monthly payment, loan amount after down payment, total interest paid over the life of the loan, and total cost.
Enter your home price, down payment percentage, interest rate, and loan term to model different scenarios instantly. The calculator runs entirely in your browser — no sign-up required and no financial data leaves your device. Note that this tool covers principal and interest only; actual mortgage payments also include property taxes, homeowners insurance, and possibly private mortgage insurance (PMI) if your down payment is less than 20%.
How to Use the Mortgage Calculator
Start by entering the home price — the total purchase price of the property. Next, set your down payment as a percentage of the home price (20% is a common default that avoids PMI). Enter the annual interest rate quoted by your lender and choose your loan term in years (15 or 30 are the most common). Results update immediately, showing your monthly payment, loan amount, total interest, and total cost. Adjust the down payment or term to compare scenarios — for example, see how putting 10% down versus 20% down affects your monthly payment and total interest.
Who Uses a Mortgage Calculator?
- First-time home buyers determine how much house they can afford before starting their search.
- Real estate agents run quick payment estimates for clients comparing properties at different price points.
- Refinancing homeowners compare their current loan against new rates to decide if refinancing makes financial sense.
- Investors model cash flow on rental properties by estimating principal and interest costs.
- Financial planners help clients understand the long-term cost of different down payment and term strategies.
Key Features
- Monthly payment, loan amount, total interest, and total cost at a glance
- Down payment percentage automatically reduces the loan principal
- Standard amortization formula for fixed-rate mortgages
- Real-time updates as you adjust price, down payment, rate, or term
- Runs entirely in your browser — private and free with no account required
Tips for Getting the Most From This Tool
Always compare total interest paid across scenarios, not just the monthly payment. A 30-year mortgage has lower monthly payments but can cost tens of thousands more in interest than a 15-year loan. Factor in PMI if your down payment is below 20% — it typically adds $100–$300 per month until you reach 20% equity. For a complete monthly housing budget, add estimated property taxes, insurance, and HOA fees on top of the principal-and-interest figure shown here. Shop multiple lenders and enter each quoted rate to find the best deal.
Frequently Asked Questions
What does down payment percentage affect?
A larger down payment reduces the loan principal, which lowers monthly payments and total interest paid. A 20% down payment also typically eliminates the need for PMI (private mortgage insurance). Even increasing your down payment by 5% can meaningfully reduce both your monthly cost and lifetime interest.
Should I choose a 15 or 30-year mortgage?
A 15-year mortgage has higher monthly payments but significantly less total interest — often saving six figures over the life of the loan. A 30-year mortgage has lower monthly payments, freeing up cash flow for other goals, but you pay much more in interest over time. Try both terms in the calculator with your actual numbers to see the trade-off.
Does this include property taxes and insurance?
No. This calculator shows principal and interest only. Your actual monthly housing payment will also include property taxes, homeowners insurance, and possibly PMI or HOA fees. These can add 30–50% to the figure shown here depending on your location and loan terms.
How is the monthly payment calculated?
The monthly payment uses the standard amortization formula where P is the loan principal (home price minus down payment), r is the monthly interest rate (annual rate divided by 12), and n is the total number of monthly payments (years times 12). Each payment covers both interest and principal, with the interest portion decreasing over time.
Can I use this for adjustable-rate mortgages (ARMs)?
This calculator is designed for fixed-rate mortgages where the interest rate stays constant for the entire term. ARMs have rates that adjust after an initial fixed period, so your payments will change over time. Use the introductory rate as a starting estimate, but plan for potential increases.
Is my financial information stored anywhere?
No. All calculations run locally in your browser. Your home price, down payment, interest rate, and loan term are never uploaded to a server or shared with any third party.