15 or 30 Year Mortgage Calculator

Deciding between a 15-year and 30-year mortgage is a major financial decision that affects your monthly payments, total interest costs, and long-term savings. This calculator helps you compare both options by calculating monthly payments, total interest paid, and the difference in payments between the two terms.

How to Use This Calculator

To use the mortgage calculator:

Enter the loan amount you're considering
Input your current interest rate
Select either 15-year or 30-year term
Click "Calculate" to see your results

The calculator will display your monthly payment, total interest paid over the loan term, and a comparison between the two options. You can also view a chart showing the interest paid over time for each term.

Mortgage Payment Formula

The monthly mortgage payment is calculated using the standard amortization formula:

M = P [i(1 + i)ⁿ] / [(1 + i)ⁿ - 1]

Where:

M = Monthly payment
P = Principal loan amount
i = Monthly interest rate (annual rate divided by 12)
n = Number of payments (loan term in years × 12)

This formula accounts for the interest on both the original principal and the interest accumulated over the life of the loan.

15-Year vs 30-Year Mortgage Comparison

Here's a comparison of key differences between 15-year and 30-year mortgages:

Feature	15-Year Mortgage	30-Year Mortgage
Monthly payments	Higher (pay off more principal each month)	Lower (spread payments over longer term)
Interest costs	Lower total interest paid	Higher total interest paid
Loan term	15 years	30 years
Refinancing options	Less common	More common
Risk	Higher risk if interest rates rise	Lower risk if interest rates rise

For example, a $200,000 loan at 4% interest would have monthly payments of $1,631 for 15 years versus $995 for 30 years. The 15-year option would save you about $28,000 in interest over the life of the loan.

Frequently Asked Questions

Which mortgage term is better?: The best term depends on your financial situation. A 15-year mortgage can save you money on interest but requires larger monthly payments. A 30-year mortgage offers lower monthly payments but costs more in interest over time.
Can I switch between 15-year and 30-year terms?: Yes, you can refinance your mortgage to change the term, but this typically requires good credit and may have fees. It's best to consider this option when you're ready to refinance.
What happens if interest rates rise?: If interest rates increase, your monthly payments will rise if you have an adjustable-rate mortgage (ARM). With a fixed-rate mortgage, your payments remain the same regardless of rate changes.
Are there any penalties for paying off early?: Some mortgages have prepayment penalties, but many conventional loans allow you to pay off early without penalty. Always check your loan agreement.
What's the minimum down payment for each term?: Down payment requirements vary by lender, but generally you'll need at least 3% for a 30-year mortgage and 5% for a 15-year mortgage. Some lenders offer lower down payment options.