Mortgage Payment Calculator & Formula
The monthly mortgage payment formula is M = P[r(1+r)^n]/[(1+r)^n – 1], where P is the principal loan amount, r is the monthly interest rate (annual rate ÷ 12), and n is the total number of monthly payments. Use our calculator below to get your exact payment instantly.
The Mortgage Payment Formula Explained
The standard mortgage payment formula used by every lender in the United States is:
M = P[r(1+r)n] / [(1+r)n – 1]
Where M is your monthly payment, P is the principal (the amount you borrow), r is your monthly interest rate (divide the annual rate by 12), and n is the total number of payments (loan term in years × 12). For example, a $300,000 loan at 6.5% for 30 years means P = 300,000, r = 0.065/12 = 0.005417, and n = 360.
Monthly Payment Examples by Loan Amount and Interest Rate
| Loan Amount | 4.5% Rate | 5.5% Rate | 6.5% Rate | 7.5% Rate |
|---|---|---|---|---|
| $200,000 | $1,013 | $1,136 | $1,264 | $1,398 |
| $300,000 | $1,520 | $1,703 | $1,896 | $2,098 |
| $400,000 | $2,027 | $2,271 | $2,528 | $2,797 |
| $500,000 | $2,533 | $2,839 | $3,160 | $3,496 |
All examples assume a 30-year fixed-rate mortgage with principal and interest only (no taxes or insurance).
Understanding Your Mortgage Payment
Your monthly mortgage payment has four main components. Principal is the amount you borrow. Interest is what the lender charges to loan you that money. Property taxes go to your local government and are typically escrowed by the lender. Homeowners insurance protects the property and is also usually escrowed.
Most people focus on the principal and interest portion because those are fixed for the life of a conventional loan. Taxes and insurance can fluctuate annually based on property values and insurance costs. HOA fees, if applicable, are separate from the mortgage but factor into your total housing cost.
Lenders look at your full PITI payment when determining how much house you can afford. They typically want your PITI to be no more than 28% of your gross monthly income, though this can vary by loan program and lender.
How Interest Rates Impact Your Payment
Small changes in interest rates create surprisingly large differences in your monthly payment and total interest paid. On a $300,000 loan over 30 years, the difference between 6% and 7% is about $180 per month and over $65,000 in total interest.
That's why rate shopping matters. Getting quotes from multiple lenders can save you thousands. Even a quarter-point difference adds up over 30 years. Your credit score plays a major role in the rate you qualify for, so improving your score before applying can pay off.
Fixed-rate mortgages lock in your rate for the entire term. Adjustable-rate mortgages (ARMs) start with a lower rate that can change after an initial period. ARMs carry more risk but can make sense if you plan to move or refinance before the rate adjusts.
15-Year vs 30-Year Mortgages
The most common mortgage terms are 15 and 30 years. A 15-year mortgage has higher monthly payments but costs far less in total interest. On a $300,000 loan at 6%, the 15-year payment is about $2,532 versus $1,799 for the 30-year. But the 15-year saves you over $155,000 in interest.
Most people choose 30 years because the lower payment is easier to manage. You can always pay extra toward principal to shorten the term without committing to the higher required payment. This gives you flexibility if money gets tight.
One strategy is to get a 30-year loan but make payments as if it were a 15-year. You pay it off faster and save on interest, but you're not locked into the higher payment if your financial situation changes.
Frequently Asked Questions
What is the mortgage payment formula?
The mortgage payment formula is M = P[r(1+r)^n]/[(1+r)^n - 1]. M is the monthly payment, P is the loan principal, r is the monthly interest rate (annual rate divided by 12), and n is the total number of monthly payments (years times 12).
How do you calculate monthly mortgage payment manually?
To calculate manually: 1) Convert annual rate to monthly by dividing by 12. 2) Multiply loan years by 12 to get total payments. 3) Plug values into M = P[r(1+r)^n]/[(1+r)^n - 1]. For a $250,000 loan at 6% for 30 years: r = 0.005, n = 360, monthly payment = $1,499.
What is the monthly payment on a $300,000 mortgage?
On a $300,000 30-year fixed mortgage, monthly payments range from $1,520 at 4.5% to $2,098 at 7.5%. At the current average rate of around 6.5%, expect to pay approximately $1,896 per month for principal and interest only.
What does PITI stand for?
PITI stands for Principal, Interest, Taxes, and Insurance. It represents the full monthly housing payment most mortgage lenders use to qualify borrowers.
How is the monthly payment calculated?
The calculator uses the standard mortgage formula: M = P[r(1+r)^n]/[(1+r)^n - 1], where P is principal, r is monthly interest rate, and n is number of payments.
Does this include PMI?
No. Private Mortgage Insurance (PMI) varies by lender and down payment. Add your PMI quote to the insurance field if you have one.
Can I see an amortization schedule?
This calculator shows totals. For a detailed payment-by-payment breakdown, use our mortgage amortization calculator.
What if I make extra payments?
Extra payments reduce your principal and total interest paid. Check our mortgage extra payment calculator to see how much you can save.