30 Year Mortgage Calculator

Reviewed and validated by David Chen, CFA. This calculator uses industry-standard compound interest formulas.

The 30 Year Mortgage Calculator helps you quickly estimate your monthly principal and interest payment, as well as the total interest paid over the life of a long-term home loan. Adjust the loan amount, interest rate, and term to see how they impact your finances.

30 Year Mortgage Calculator

Estimated Monthly Payment (P&I) $0.00

Detailed Calculation Steps

Click 'Calculate' to see the detailed steps.

30 Year Mortgage Calculator Formula

The standard fixed-rate mortgage payment formula is:

M = P [ r(1 + r)ⁿ / ( (1 + r)ⁿ – 1 ) ]

Where: M = Monthly Payment, P = Principal Loan Amount, r = Monthly Interest Rate, and n = Total Number of Months. Formula Sources: Investopedia, Bankrate

Variables

The calculation requires three key variables:

• Loan Amount (P): The total amount of money borrowed. This is the home’s price minus your down payment.
• Annual Interest Rate (R): The yearly cost of the loan, expressed as a percentage. This rate is used to determine the monthly interest.
• Loan Term (N): The total duration of the loan, typically 30 years for this calculator, but can be adjusted. This is converted into total number of payments (months).

Related Calculators

Explore other financial tools to help manage your home ownership journey:

• Amortization Schedule Generator (Internal Link 1)
• Loan Refinance Breakeven Calculator (Internal Link 2)
• Debt-to-Income Ratio Calculator (Internal Link 3)
• Closing Cost Estimator (Internal Link 4)

What is a 30 Year Mortgage?

A 30-year fixed-rate mortgage is a loan structure where the interest rate remains the same for the entire 30-year (360-month) term. It is the most common type of mortgage in the U.S. because it offers the lowest monthly payments compared to shorter terms (like 15 years), making homeownership more accessible.

While the monthly payments are lower, the long term means you accrue and pay significantly more interest over the loan’s life. The first few years of payments go almost entirely toward interest, with only a small fraction reducing the principal balance.

How to Calculate a 30-Year Mortgage (Example)

Let’s calculate the monthly payment for a $200,000 loan at a 4.5% annual rate over 30 years:

1. Determine Monthly Rate (r): Convert the annual rate (4.5%) to a decimal (0.045), then divide by 12: $0.045 / 12 = 0.00375$.
2. Determine Total Payments (n): Multiply the term in years (30) by 12: $30 \times 12 = 360$ payments.
3. Calculate the Numerator Factor: Calculate $(1 + r)^n$. In this case, $(1 + 0.00375)^{360} \approx 3.8288$.
4. Apply the Formula: $M = \$200,000 \times [ 0.00375 \times 3.8288 / ( 3.8288 – 1 ) ]$.
5. Solve for M: $M \approx \$200,000 \times [ 0.014358 / 2.8288 ] \approx \$200,000 \times 0.0050756$.
6. Final Monthly Payment: The estimated monthly payment is $M \approx \$1,015.13$.

Frequently Asked Questions (FAQ)

Is a 30-year mortgage worth it?

A 30-year mortgage offers the benefit of low monthly payments, providing maximum flexibility and improving monthly cash flow. However, you will pay significantly more in total interest compared to a 15-year loan.

How much interest do I pay on a $300,000 loan over 30 years?

This depends entirely on the interest rate. At a 6.0% rate, the total interest paid would be approximately $347,517, meaning you would pay more in interest than the principal loan amount itself.

What is the difference between P&I and the full payment?

P&I stands for Principal and Interest, which is what this calculator estimates. The full monthly payment, often called PITI, also includes Property Taxes, Homeowner’s Insurance, and sometimes Private Mortgage Insurance (PMI).

How does the Loan Term affect the interest rate?

Generally, shorter loan terms (like 15 years) carry a slightly lower interest rate than longer terms (like 30 years) because the lender’s risk is lower over a shorter time frame.