Before you sign anything, it helps to know how to calculate your monthly mortgage payment. The result is a planning estimate based on the assumptions you enter, broken down so you can see where each part of the monthly housing cost comes from.
This guide walks through the calculation step by step, explains the standard fully amortizing fixed-rate formula, and shows what may be included beyond principal and interest.
Quick Answer: How do you calculate a monthly mortgage payment? Use the formula: M = L × [r(1+r)^n] / [(1+r)^n − 1] where M is the monthly principal-and-interest payment, L is the loan amount, r is the monthly interest rate, and n is the number of payments. For a $320,000 loan at 6.75% for 30 years, estimated principal and interest is $2,075.51/month (about $2,076). Adding $400 in property tax, $150 in homeowners insurance, $150 in HOA dues, and $0 in PMI produces an estimated total monthly housing cost of $2,775.51 (about $2,776).
What Goes Into a Mortgage Payment?
A mortgage loan payment starts with principal and interest, while the total monthly housing cost may include several additional expenses. Keeping these categories separate makes the estimate easier to understand.
The five cost categories to budget for:
| Component | What It Is | How It Is Usually Paid |
|---|---|---|
| Principal & interest (P&I) | Repayment of the loan balance plus the cost of borrowing | The base mortgage loan payment |
| Property taxes | Taxes assessed on the property | Often collected through lender escrow |
| Homeowners insurance | Coverage for the home and qualifying risks | Often collected through lender escrow |
| PMI | Private mortgage insurance that may apply to some conventional loans | Often included in the amount paid to the lender when required |
| HOA dues | Fees charged by a homeowners association | Usually paid separately and generally not included in lender escrow |
Many lenders collect property taxes and homeowners insurance through an escrow account and pay those bills on the borrower's behalf. PMI may also be collected with the monthly loan payment when it applies. HOA dues are not part of P&I and are usually paid separately rather than through lender escrow, but they still belong in a total monthly housing-cost estimate.
The Mortgage Payment Formula
The standard formula for calculating monthly mortgage principal and interest is:
M = L × [r(1 + r)^n] / [(1 + r)^n − 1]
Where:
- M = Monthly payment
- L = Loan amount (home price minus down payment)
- r = Monthly interest rate (annual rate ÷ 12)
- n = Total number of payments (loan term in years × 12)
This is the standard formula for a fully amortizing fixed-rate mortgage, and it is the formula behind our Mortgage Calculator. It calculates P&I only; taxes, insurance, PMI, and HOA dues are separate inputs.
Step-by-Step: How to Calculate Your Monthly Mortgage Payment
Let's work through a real example.
Scenario:
- Home price: $400,000
- Down payment: $80,000 (20%)
- Loan amount: $320,000
- Annual interest rate: 6.75%
- Loan term: 30 years
- Property tax: $4,800/year ($400/month)
- Homeowners insurance: $1,800/year ($150/month)
- HOA dues: $150/month
- PMI: $0
Step 1: Calculate the loan amount
Loan amount = Home price − Down payment
Loan amount = $400,000 − $80,000 = $320,000
Step 2: Find the monthly interest rate
Divide the annual interest rate by 12:
r = 6.75% ÷ 12 = 0.5625% = 0.005625
Step 3: Calculate the total number of payments
Multiply the loan term in years by 12:
n = 30 × 12 = 360 payments
Step 4: Apply the mortgage payment formula
M = $320,000 × [0.005625 × (1.005625)^360] / [(1.005625)^360 − 1]
(1.005625)^360 ≈ 7.5332
M = $320,000 × [0.005625 × 7.5332454772] / [7.5332454772 − 1]
M = $320,000 × 0.0423745058 / 6.5332454772
M = $320,000 × 0.00648598097
M ≈ $2,075.51/month
The displayed power is approximately 7.5332, but retaining full precision through the calculation produces an estimated principal-and-interest payment of $2,075.51 per month, or about $2,076.
Step 5: Add other costs for your total monthly housing payment
| Component | Monthly Cost |
|---|---|
| Principal & Interest | $2,075.51 |
| Property tax ($4,800/year) | $400 |
| Homeowners insurance ($1,800/year) | $150 |
| HOA dues | $150 |
| PMI (assumed in this example) | $0 |
| Total monthly housing payment | $2,775.51 |
The difference between the base P&I payment ($2,075.51) and the total monthly housing payment ($2,775.51) is $700. Of that amount, property taxes and homeowners insurance may be escrowed, while the $150 HOA dues are generally paid separately. Over 360 scheduled payments, estimated principal and interest paid totals $747,185.01, including $427,185.01 in interest. These loan-term totals exclude taxes, insurance, HOA dues, and PMI because those costs can change over time.
How Interest Rate Affects Your Monthly Payment
Interest rate can materially affect both monthly P&I and total interest. Even a 0.5-percentage-point difference can have a substantial impact over 30 years.
$320,000 loan, 30-year term — monthly P&I at different rates:
| Interest Rate | Monthly P&I | Total Interest Paid |
|---|---|---|
| 5.00% | $1,717.83 | $298,418.51 |
| 5.50% | $1,816.92 | $334,092.93 |
| 6.00% | $1,918.56 | $370,682.20 |
| 6.75% | $2,075.51 | $427,185.01 |
| 7.00% | $2,128.97 | $446,428.47 |
| 7.50% | $2,237.49 | $485,495.11 |
| 8.00% | $2,348.05 | $525,296.79 |
Holding the loan amount and term constant, the difference between a 5% and 7.5% rate is $519.66/month and $187,076.60 in total interest over 30 years. Actual rates and loan costs depend on lender pricing, borrower qualifications, and market conditions.
How Loan Term Affects Your Monthly Payment
The loan term — 15 years vs. 30 years — dramatically changes both what you pay each month and how much you pay in total interest.
$320,000 loan at 6.75%:
| Loan Term | Monthly P&I | Total Interest | Total Cost |
|---|---|---|---|
| 10 years | $3,674.37 | $120,924.60 | $440,924.60 |
| 15 years | $2,831.71 | $189,707.85 | $509,707.85 |
| 20 years | $2,433.16 | $263,959.56 | $583,959.56 |
| 30 years | $2,075.51 | $427,185.01 | $747,185.01 |
A 15-year mortgage at the same rate has $756.20 more in monthly P&I than a 30-year mortgage but $237,477.16 less in total interest. Whether that trade-off fits depends on your income, other financial goals, and cash-flow needs.
In this table, Total Cost means total scheduled principal and interest for the loan. It does not include the down payment, property taxes, homeowners insurance, PMI, HOA dues, closing costs, or other ownership expenses.
How Down Payment Affects Your Monthly Payment
A larger down payment reduces your loan amount and may allow you to avoid PMI on many conventional loans at 20% down, although loan-program and lender rules vary.
$400,000 home, 6.75% rate, 30-year term:
| Down Payment | % Down | Loan Amount | Monthly P&I | Estimated PMI | P&I + Estimated PMI |
|---|---|---|---|---|---|
| $20,000 | 5% | $380,000 | $2,464.67 | $190.00 | $2,654.67 |
| $40,000 | 10% | $360,000 | $2,334.95 | $180.00 | $2,514.95 |
| $60,000 | 15% | $340,000 | $2,205.23 | $170.00 | $2,375.23 |
| $80,000 | 20% | $320,000 | $2,075.51 | $0 | $2,075.51 |
| $100,000 | 25% | $300,000 | $1,945.79 | $0 | $1,945.79 |
For a consistent comparison, the table uses an illustrative annual PMI cost of 0.6% of the loan amount when the down payment is below 20%; actual PMI eligibility and pricing vary. Under those assumptions, moving from 5% to 20% down reduces monthly P&I by $389.16 and removes the $190 illustrative PMI amount, reducing modeled P&I plus PMI by $579.16. Property taxes, homeowners insurance, and HOA dues are excluded from this table.
What Is PMI and When Do You Need It?
Private Mortgage Insurance (PMI) may be required on a conventional loan when the down payment is below 20% of the home's value. It protects the lender — not the borrower — if the borrower defaults. Requirements differ for other loan types and programs.
For illustration, the comparison above assumes annual PMI equal to 0.6% of the original loan amount, divided into monthly payments. That is an example assumption, not a quote; actual PMI pricing depends on the loan, borrower, property, insurer, and lender.
Example: On a $380,000 loan at 0.6% PMI:
Annual PMI = $380,000 × 0.006 = $2,280
Monthly PMI = $2,280 ÷ 12 = $190/month
For many conventional mortgages covered by federal PMI cancellation rules, you may request cancellation when the principal balance reaches 80% of the home's original value, subject to requirements such as a written request, current payments, a good payment history, and any evidence the servicer requires. Automatic termination is generally tied to the date the balance is scheduled to reach 78% of the original value, provided payments are current. Home-price appreciation does not by itself trigger automatic cancellation, although some loan investors or servicers may offer separate cancellation paths based on current value. Rules vary by loan type, lender, investor, and servicer, so review the Consumer Financial Protection Bureau's PMI cancellation guidance, check your PMI disclosure, and contact your servicer.
How to Lower Your Mortgage Payment
If the payment calculation comes out higher than expected, these are several ways to model a lower payment:
Increase your down payment Holding the rate and term constant, a larger down payment reduces the loan amount and therefore lowers P&I. In the table above, moving from 10% to 20% down reduces P&I by $259.44/month and removes the $180/month illustrative PMI assumption. Whether PMI applies depends on the loan program and lender.
Lock in a lower interest rate A lower interest rate reduces P&I when the loan amount and term stay the same. Compare offers using both the interest rate and APR, along with points and fees; the rate available to any borrower depends on lender pricing, market conditions, loan details, and borrower qualifications.
Choose a longer loan term Holding the loan amount and rate constant, a 30-year term has lower monthly P&I than a 15-year term, though it produces more total interest in the comparison above.
Buy a less expensive home If the down payment stays the same, a lower home price reduces the amount borrowed. At 6.75% for 30 years, reducing the loan amount by $50,000 lowers monthly P&I by approximately $324.30.
Buy down the rate with points Paying discount points upfront may lower your interest rate. One point generally costs 1% of the loan amount, but the actual rate reduction depends on lender pricing and market conditions; it is not always 0.25 percentage points. Compare the upfront cost with the projected monthly savings and how long you expect to keep the loan.
Use the Mortgage Calculator to Run Your Numbers
The formula above gives you the methodology — the Mortgage Calculator gives you a planning estimate for any combination of loan amount, interest rate, term, and additional costs.
If you want the broader context around payment structure, term tradeoffs, and full ownership costs, the Mortgage Payments and Costs topic page is the best next read.
Open the Mortgage Calculator — enter your home price, down payment, interest rate, loan term, taxes, insurance, HOA dues, and optional PMI to estimate your total monthly housing payment.
Frequently Asked Questions
What is the mortgage payment formula?
The standard fixed-rate mortgage payment formula is M = L × [r(1+r)^n] / [(1+r)^n − 1], where M is the monthly P&I payment, L is the loan amount, r is the monthly interest rate (annual rate ÷ 12), and n is the total number of payments (years × 12). This calculates principal and interest only. Add property taxes, homeowners insurance, PMI when applicable, and HOA dues to estimate total monthly housing cost.
How much is a mortgage payment on a $300,000 house?
Assuming a 20% down payment ($60,000), a $240,000 loan at 6.75% for 30 years produces estimated P&I of $1,556.64/month. A total monthly housing-cost estimate cannot be determined from the home price alone: add property taxes, homeowners insurance, HOA dues, and PMI if applicable. Use the Mortgage Calculator to model those assumptions for the property and loan you are considering.
What percentage of income should go to a mortgage?
The 28/36 rule is a commonly cited budgeting guideline: housing expenses at roughly 28% or less of gross monthly income and total debt payments at roughly 36% or less. It is not a universal approval rule or a guarantee of affordability. Underwriting limits and calculations vary by lender and loan program, and your own budget should account for take-home pay, savings, maintenance, and other goals.
Does a higher down payment always lower my monthly payment?
Holding the home price, interest rate, and term constant, a higher down payment reduces the loan amount and lowers P&I. Reaching 20% down may also avoid PMI on many conventional loans, but rules differ by loan type and lender. A higher down payment leaves less cash available for emergencies, closing costs, repairs, or other goals, so evaluate the trade-off carefully.
How does my credit score affect my mortgage payment?
Credit score is one factor lenders may use when pricing a mortgage, but no particular score guarantees a specific rate. The offered rate can also depend on the loan program, loan-to-value ratio, property, points, lender pricing, market conditions, and other borrower qualifications. Compare written Loan Estimates rather than assuming a rate from a credit-score range alone.
What is an escrow account in a mortgage?
An escrow account is an account your lender or servicer may use to collect and pay property taxes and homeowners insurance on your behalf. Each month, a portion of the amount paid to the lender goes into escrow. When a covered bill is due, the servicer pays it from the account. HOA dues are generally separate from lender escrow, even though they remain part of your monthly housing budget.
Key Takeaways
- The standard fully amortizing fixed-rate mortgage formula is M = L × [r(1+r)^n] / [(1+r)^n − 1], and it calculates P&I rather than every housing cost
- Your total monthly housing cost can include P&I, property taxes, homeowners insurance, PMI, and HOA dues; HOA is not part of P&I and is generally paid outside lender escrow
- In the worked example, a $320,000 loan at 6.75% for 30 years has estimated P&I of $2,075.51/month and a total monthly housing payment of $2,775.51 after $400 in taxes, $150 in insurance, $150 in HOA dues, and $0 in PMI
- Over the full term, estimated principal and interest totals $747,185.01, including $427,185.01 in interest; these totals exclude taxes, insurance, HOA dues, and PMI
- A 20% down payment may avoid PMI on many conventional loans, but requirements and cancellation rules vary
- The 15-year vs. 30-year trade-off: lower total interest vs. lower monthly payment — depends on your cash flow
- Use the Mortgage Calculator to create a planning estimate for your own assumptions
This article is for informational purposes only and does not constitute financial advice. Please consult a qualified financial advisor or mortgage professional before making home buying decisions.