How a Mortgage Payment Is Calculated
A standard mortgage payment in the US and UK consists of four components, often abbreviated as PITI:
- Principal — the portion that pays down your loan balance
- Interest — the lender's charge for lending you money
- Taxes — property taxes collected and paid by your lender
- Insurance — homeowner's insurance (and PMI if down payment is under 20%)
In the early years of your mortgage, the vast majority of each payment goes toward interest. Over time, as your balance decreases, more goes toward principal. This is called amortization.
On a $350,000 30-year mortgage at 6.5%, your first payment of $2,212 includes roughly $1,896 in interest and only $316 in principal. By year 15, it flips — you're paying more principal than interest.
The Mortgage Payment Formula Explained
The formula for calculating your monthly principal and interest payment is:
M = P × [r(1+r)^n] ÷ [(1+r)^n − 1]
Where: M = monthly payment · P = principal loan amount · r = monthly interest rate (annual rate ÷ 12) · n = total number of payments (years × 12)
For a $300,000 loan at 6.5% for 30 years: r = 0.065/12 = 0.00542, n = 360. This gives a monthly payment of $1,896 in principal and interest.
What Factors Affect Your Mortgage Rate in 2026
| Factor | Impact on Rate | US Average 2026 |
|---|---|---|
| Credit Score 760+ | Lowest rates | 6.2% – 6.6% |
| Credit Score 700–759 | Average rates | 6.6% – 7.0% |
| Credit Score 640–699 | Higher rates | 7.0% – 7.8% |
| 20%+ Down Payment | No PMI, better rate | Saves $150–$300/mo |
| 15-Year vs 30-Year | 0.5–0.75% lower | Higher monthly payment |
| FHA Loan | Low down payment | Requires MIP premium |
How Much Mortgage Can You Afford?
Lenders use two key ratios to determine how much you can borrow:
The 28% Front-End Rule
Your total housing payment (PITI) should not exceed 28% of your gross monthly income. On a $80,000 annual salary, that's $1,867/month maximum housing payment.
The 36% Back-End Rule (Debt-to-Income)
All monthly debt payments combined — mortgage, car, student loans, credit cards — should not exceed 36% of gross monthly income (some lenders allow up to 43% for qualified borrowers).
| Annual Salary | Max Monthly Payment (28%) | Estimated Loan Amount |
|---|---|---|
| $60,000 | $1,400 | ~$210,000 |
| $80,000 | $1,867 | ~$280,000 |
| $100,000 | $2,333 | ~$350,000 |
| $150,000 | $3,500 | ~$525,000 |
| $200,000 | $4,667 | ~$700,000 |
Calculate Your Exact Mortgage Payment
Use FinCalc's free mortgage calculator — see your monthly payment, total interest and full amortization schedule in seconds.
Use Free Mortgage Calculator →Understanding Your Amortization Schedule
An amortization schedule shows every single payment over the life of your loan — how much goes to interest, how much to principal, and what your remaining balance is after each payment.
On a 30-year $350,000 mortgage at 6.5%:
- You'll make 360 payments totaling approximately $795,000
- You'll pay $445,000 in interest — more than the original loan amount
- At year 10, you'll still owe $291,000 — you've only paid off 17% of the principal
5 Ways to Pay Off Your Mortgage Faster
- Make biweekly payments — pay half your monthly payment every two weeks. This results in 13 full payments per year instead of 12, shaving 4–6 years off a 30-year mortgage.
- Round up your payment — paying just $100 extra per month on a $300,000 mortgage saves $30,000+ in interest and cuts 4 years off your loan.
- Refinance to a shorter term — switching from a 30-year to 15-year typically saves hundreds of thousands in interest, though monthly payments are higher.
- Apply windfalls to principal — tax refunds, bonuses and inheritances applied directly to principal have an outsized impact early in your loan.
- Eliminate PMI as soon as possible — once you hit 20% equity, request PMI removal. This can save $100–$300/month immediately.
Frequently Asked Questions
What is a good mortgage interest rate in 2026?
As of April 2026, the average 30-year fixed mortgage rate in the US is approximately 6.5–7.0%. A rate below 6.5% is considered excellent and typically requires a credit score of 760+ and 20%+ down payment. Rates vary by lender, so always compare at least 3–5 offers before committing.
Is it better to get a 15-year or 30-year mortgage?
A 15-year mortgage has lower interest rates (typically 0.5–0.75% less) and you pay far less total interest — but monthly payments are 30–40% higher. A 30-year gives lower monthly payments and more flexibility, but costs significantly more over time. If you can comfortably afford the 15-year payment, it's almost always the better financial decision.
How much do I need for a down payment in the US?
Conventional loans typically require 5–20% down. FHA loans accept as little as 3.5% down with a 580+ credit score. VA loans (for veterans) and USDA loans (rural areas) require 0% down. However, putting less than 20% down means paying Private Mortgage Insurance (PMI) until you reach 20% equity.
How does the Bank of England base rate affect UK mortgages?
The Bank of England's base rate directly influences variable-rate and tracker mortgages in the UK. When the base rate rises, tracker mortgages immediately become more expensive. Fixed-rate mortgages are locked in for the term but new fixed-rate deals will reflect current market rates. Monitoring BoE rate decisions is essential for UK homeowners and buyers.
What is the difference between APR and interest rate on a mortgage?
The interest rate is just the cost of borrowing the principal. APR (Annual Percentage Rate) includes the interest rate plus all fees — origination fees, mortgage points, broker fees — expressed as a yearly rate. Always compare APR, not just interest rates, when shopping for a mortgage.