30 or 15 Year Fixed Mortgage Calculator

Choosing between a 30-year and 15-year fixed mortgage is one of the most important financial decisions you'll make. This calculator helps you compare the two options by showing monthly payments, total interest paid, and how much you'll save by choosing the shorter term.

How to Use This Calculator

Enter your loan amount, interest rate, and select the mortgage term (15 or 30 years). Click "Calculate" to see the results. The calculator will show you:

Monthly payment for each term
Total interest paid over the loan term
Total amount paid (principal + interest)
A comparison chart showing the interest savings

The calculator uses the standard mortgage payment formula to calculate the results. You can also see the formula used and how the calculation works in the next section.

Mortgage Payment Formula

The monthly mortgage payment is calculated using the following formula:

Mortgage Payment 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 ÷ 12)
n = Number of payments (loan term in years × 12)

This formula accounts for the fact that each monthly payment includes both principal and interest. The interest is calculated on the remaining balance, which decreases each month as principal is paid down.

Note

The calculator assumes a fixed interest rate throughout the loan term. If interest rates change, the actual payments may differ from these calculations.

30-Year vs 15-Year Mortgages

Choosing between a 30-year and 15-year fixed mortgage has significant implications for your finances. Here's a comparison of the key differences:

Feature	30-Year Fixed	15-Year Fixed
Loan Term	30 years	15 years
Monthly Payments	Lower (but over longer period)	Higher (but over shorter period)
Total Interest Paid	Higher (more interest over longer term)	Lower (less interest over shorter term)
Refinancing Options	More options available	Fewer options available
Risk	Lower risk (longer term)	Higher risk (shorter term)

As you can see, the 15-year mortgage typically results in lower total interest payments, but the monthly payments are higher. The 30-year mortgage has lower monthly payments but higher total interest costs. The best choice depends on your financial situation and goals.

Worked Example

Let's look at an example to see how the calculations work. Suppose you're considering a $200,000 mortgage with a 4% annual interest rate.

15-Year Mortgage Calculation

Using the formula:

15-Year Mortgage Example

P = $200,000

i = 4% ÷ 12 = 0.333% or 0.00333

n = 15 × 12 = 180

M = $200,000 [ 0.00333(1 + 0.00333)¹⁸⁰ ] / [ (1 + 0.00333)¹⁸⁰ - 1 ]

M ≈ $1,492.42 per month

30-Year Mortgage Calculation

Using the same formula:

30-Year Mortgage Example

P = $200,000

i = 4% ÷ 12 = 0.333% or 0.00333

n = 30 × 12 = 360

M = $200,000 [ 0.00333(1 + 0.00333)³⁶⁰ ] / [ (1 + 0.00333)³⁶⁰ - 1 ]

M ≈ $995.55 per month

Comparison

In this example:

15-year mortgage: $1,492.42/month, total interest $108,000, total paid $308,000
30-year mortgage: $995.55/month, total interest $180,000, total paid $380,000

You'll save $72,000 in interest by choosing the 15-year term, but you'll pay $496.87 more per month.

Frequently Asked Questions

Which mortgage term is better, 15-year or 30-year?: There's no single "better" option. A 15-year mortgage saves on interest but requires higher monthly payments. A 30-year mortgage has lower monthly payments but higher total interest costs. The best choice depends on your financial situation and goals.
Can I change my mortgage term after taking it out?: Yes, you can refinance your mortgage to change the term. However, refinancing typically requires good credit and may have fees. It's important to consider the costs and benefits before making any changes.
What happens if interest rates rise after I take out my mortgage?: If interest rates rise, you may be able to refinance to take advantage of lower rates. However, if you have a fixed-rate mortgage, your payments won't change. If you have an adjustable-rate mortgage (ARM), your payments may increase.
Are there any penalties for paying off a 30-year mortgage early?: Some lenders charge prepayment penalties for paying off a mortgage early. However, many lenders now offer mortgages without prepayment penalties. Always check your loan agreement to understand any prepayment terms.
What factors should I consider when choosing a mortgage term?: Consider your financial goals, risk tolerance, and ability to make higher monthly payments. If you expect to sell or refinance soon, a shorter term might make sense. If you want lower monthly payments and can afford the higher total interest costs, a longer term might be better.