What Is a Mortgage?
A mortgage is a loan specifically used to purchase real estate. The property itself serves as collateral, meaning if the borrower fails to make payments, the lender can seize the home through a process called foreclosure. Mortgages are among the largest financial commitments most people make in their lifetime, typically spanning 15 to 30 years.
The most common type is a fixed-rate mortgage, where the interest rate remains the same for the entire loan term, providing predictable monthly payments. This calculator focuses on fixed-rate mortgages and breaks down your payment into principal, interest, taxes, insurance, and PMI (if applicable).
How Mortgage Payments Work
Your monthly mortgage payment is commonly described using the acronym PITI:
- Principal — The portion that reduces your outstanding loan balance. Early in the loan, this is small relative to interest.
- Interest — The cost of borrowing money. This is calculated on the remaining balance each month, so it decreases over time as principal is paid down.
- Taxes — Property taxes assessed by your local government, typically collected monthly by the lender and held in an escrow account.
- Insurance — Homeowners insurance protects against damage or loss. Lenders require it as a condition of the loan.
If your down payment is less than 20% of the purchase price, lenders typically require Private Mortgage Insurance (PMI), which protects the lender if you default. PMI is usually 0.3% to 1.5% of the loan amount annually and can be removed once you reach 20% equity.
The Mortgage Payment Formula
- M= Monthly principal & interest payment
- P = Loan principal (home price minus down payment)
- r = Monthly interest rate (annual rate / 12)
- n= Total number of monthly payments (years × 12)
Fixed-Rate vs. Adjustable-Rate Mortgages
| Feature | Fixed-Rate | Adjustable-Rate (ARM) |
|---|---|---|
| Interest Rate | Stays the same for the entire term | Fixed for an initial period, then adjusts periodically |
| Monthly Payment | Predictable, never changes (P&I portion) | Can increase or decrease after the initial period |
| Initial Rate | Typically higher than ARM initial rate | Often lower initially, making it attractive short-term |
| Best For | Long-term homeowners seeking stability | Those planning to sell or refinance within a few years |
| Risk Level | Low — no surprises | Higher — payments may rise significantly |
Tips for First-Time Homebuyers
Save for a Larger Down Payment
Putting down 20% or more eliminates PMI and reduces your monthly payment. Even an extra 5% can save thousands over the loan's life.
Shop Multiple Lenders
Interest rates can vary significantly between lenders. Get quotes from at least three — banks, credit unions, and online lenders — to find the best rate.
Get Pre-Approved Early
A pre-approval letter shows sellers you're a serious buyer and gives you a clear budget. It also locks in a rate for 60–90 days.
Consider Total Cost, Not Just Monthly Payment
A longer term means lower monthly payments but more total interest paid. Use the amortization schedule above to compare scenarios.
Budget for Closing Costs
Expect to pay 2–5% of the home price in closing costs (appraisal, title insurance, origination fees). These are in addition to your down payment.
Check Your Credit Score First
A higher credit score qualifies you for lower interest rates. Aim for 740+ for the best rates. Fix errors on your credit report before applying.
Frequently Asked Questions
Your monthly payment is calculated using the standard amortization formula: M = P[r(1+r)^n]/[(1+r)^n-1], 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 (loan term in years times 12). This gives the principal and interest portion. Property tax, homeowners insurance, and PMI (if applicable) are then added to get the total monthly payment.
Private Mortgage Insurance (PMI) is required by most lenders when your down payment is less than 20% of the home's purchase price. PMI protects the lender (not you) if you default on the loan. It typically costs between 0.3% and 1.5% of the original loan amount per year. You can request PMI removal once your loan-to-value ratio reaches 80%, and lenders are required to automatically cancel it at 78% LTV.
A 15-year mortgage has higher monthly payments but significantly less total interest paid over the life of the loan. A 30-year mortgage has lower monthly payments, giving you more flexibility in your budget, but you'll pay substantially more in interest. For example, on a $280,000 loan at 6.5%, a 30-year mortgage costs about $357,000 in interest, while a 15-year mortgage costs about $157,000 — a difference of $200,000. Choose based on what fits your budget and financial goals.
A common guideline is the 28/36 rule: spend no more than 28% of your gross monthly income on housing costs (mortgage payment, taxes, insurance) and no more than 36% on total debt payments (housing plus car loans, student loans, credit cards). For example, if you earn $6,000/month gross, aim for a total housing payment under $1,680. Use this calculator to find a home price that fits within that budget.
Amortization is the process of paying off a loan through regular payments over time. Each payment is split between principal (reducing the loan balance) and interest (the cost of borrowing). In the early years of a mortgage, most of each payment goes toward interest. Over time, the interest portion decreases and the principal portion increases. The amortization schedule above shows exactly how each payment is allocated month by month.
No, this calculator is designed for fixed-rate mortgages only, where the interest rate remains the same for the entire loan term. Adjustable-rate mortgages (ARMs) have variable rates that change after an initial fixed period, making them more complex to calculate. For ARM estimates, you would need to model different rate scenarios for each adjustment period.
A larger down payment reduces your loan amount, which lowers your monthly payment and the total interest paid over the life of the loan. Putting down at least 20% also eliminates the need for PMI, saving you an additional monthly expense. For example, on a $350,000 home, increasing your down payment from 10% ($35,000) to 20% ($70,000) saves you roughly $200/month in principal and interest, plus eliminates PMI of approximately $115/month.
This calculator provides accurate estimates based on the standard fixed-rate mortgage amortization formula used by lenders. The principal and interest calculation is exact. However, actual costs may vary because property tax rates change annually, insurance premiums depend on coverage and provider, and your actual interest rate depends on your credit score, loan type, and market conditions. Use this as a planning tool and consult with a lender for exact figures.
Closing costs are fees paid when finalizing your home purchase, typically ranging from 2% to 5% of the home price. They include appraisal fees, title insurance, origination fees, attorney fees, and prepaid items like initial escrow deposits. This calculator does not include closing costs in its calculations — it focuses on the ongoing monthly payment. Budget for closing costs separately when planning your home purchase.
Yes, completely. This mortgage calculator runs 100% in your web browser using JavaScript. No financial data, home prices, income information, or any other inputs are sent to any server. All calculations happen locally on your device. There is no account required, no tracking of your inputs, and nothing is stored after you close the page.