15-Year Home Loan Interest and Monthly Payment Calculator

This calculator estimates the monthly principal-and-interest payment and total interest for a fixed-rate loan repaid over 15 years. Enter the loan amount and the APR offered by your lender; the results do not include taxes, insurance, or other housing costs.

Formula

The calculator uses the standard fixed-payment amortization formula. Let P be the loan principal in dollars, APR the annual percentage rate entered as a percentage, r = APR / 1200 the monthly interest rate as a decimal, and n = years × 12 the number of monthly payments. The unrounded payment is P × r / [1 − (1 + r)⁻ⁿ]. The displayed monthly payment is rounded to cents. Total interest is calculated as that rounded monthly payment multiplied by the number of payments, minus the original principal.

The phrase “15-year home loan” describes a repayment term, not one universal interest rate. The rate is an input that must come from a lender’s offer or other applicable loan disclosure. This page does not fetch live rates or determine what rate a borrower may receive. To model a 15-year term, enter 15 in the years field; the default term of 5 years is included only as a neutral calculator example.

Worked Example

Using exactly the calculator defaults: loan amount P = $20,000, APR = 8%, and term = 5 years.

1. Convert the APR to a monthly rate: r = 8 / 1200 = 0.0066667.
2. Find the number of monthly payments: n = 5 × 12 = 60.
3. Substitute into the payment formula: $20,000 × 0.0066667 / [1 − (1.0066667)⁻⁶⁰] ≈ $405.53 per month, rounded to cents.
4. Calculate total interest using the displayed payment: $405.53 × 60 − $20,000 = $4,331.80.

The example is arithmetic, not a current rate quote or an estimate of a particular home loan. For a 15-year illustration, change the term to 15 and enter the actual principal and APR you want to examine.

Assumptions

• The interest rate remains fixed for the full term.
• There are equal monthly payments, made at the end of each monthly period.
• Interest accrues monthly using APR divided by 12; the formula assumes monthly compounding.
• The calculation covers principal and interest only. It excludes lender fees, taxes, homeowners insurance, mortgage insurance, escrow, and any other charges.

What a 15-Year Term Changes

For a given principal and rate, a 15-year term has fewer scheduled payments than a longer term. Since the principal must be repaid in less time, its monthly principal-and-interest payment is generally higher than the payment for a longer term at the same rate. The loan also has less time to accrue interest, so the total interest calculated over the scheduled term is generally lower, assuming the same principal, rate, and payment schedule.

That comparison is not a complete measure of housing cost. A mortgage payment can also include amounts collected for taxes, insurance, or mortgage insurance, and those items are outside this calculator. A shorter term’s higher scheduled payment may also matter more to a household’s monthly cash flow than the interest total does. The calculator cannot assess income, other debts, savings, property costs, or loan approval.

How to Use the Results

• Loan amount: Enter the principal being borrowed, not the home’s purchase price unless the entire price is financed.
• Interest rate (APR): Enter the annual rate as a percentage, such as 6.5 for 6.5%. Do not enter 0.065. Use the specific figure and rate assumptions supplied for the loan you are modelling.
• Loan term: Enter years. For a 15-year scenario, enter 15. The permitted calculator range is broader so that other fixed-term examples can also be checked.
• Monthly payment: This is the calculated principal-and-interest amount, rounded to the nearest cent. It is not necessarily the total amount due each month.
• Total interest: This is the sum of the rounded scheduled payments less the original principal, assuming all payments are made as scheduled and no extra payments or charges are added.

Rounding creates a small distinction between an ideal mathematical payment and a real servicing schedule. A lender may adjust the final payment to account for cents, payment dates, or its precise interest calculation. The estimate should therefore be treated as a comparison tool, not a payoff statement.

Common Limits and Mistakes

A common error is treating the calculator’s payment as the full mortgage bill. It omits escrowed costs, insurance, taxes, and fees. Another is using a quoted rate that is not the APR or not using the same assumptions as the disclosure. APR and interest rate are related but may represent different things; enter the rate specified for the calculation you intend to reproduce, and consult the lender’s documents for the exact payment basis.

The formula assumes a fixed rate and regular monthly payments. It does not model an adjustable rate, skipped or late payments, extra principal, refinancing, closing costs, or a changing balance due to fees. It also does not calculate a loan’s eligibility, approval, or total cost of owning a home. For those details, obtain the figures and terms directly from the lender and include costs that are relevant to the scenario.

Frequently Asked Questions

What is the interest rate on a 15-year home loan?
There is no single rate that applies to every 15-year home loan. The rate depends on the specific loan offer and its terms. Enter the APR from the relevant lender disclosure to estimate payments; this calculator does not provide live quotes.

How do I calculate a 15-year mortgage payment?
Enter the principal, annual rate as a percentage, and 15 years. The calculator converts the APR to a monthly rate, applies the fixed-payment amortization formula, and shows the monthly principal-and-interest payment and estimated total interest.

Is a 15-year mortgage payment higher than a 30-year payment?
For the same principal and interest rate, the scheduled principal-and-interest payment is generally higher over 15 years because the balance is repaid in fewer installments. A comparison should use the same loan amount and rate assumptions.

Does the monthly payment include taxes and insurance?
No. The result includes principal and interest only. Taxes, homeowners insurance, mortgage insurance, escrow, and lender charges are not included.

Does this calculator show the current 15-year mortgage rate?
No. It calculates payments from the APR you enter and does not retrieve current market rates. Use the rate and payment details from the lender’s current disclosure for a loan-specific estimate.

This result is an estimate, and the lender’s disclosure gives the exact figures.

Related

• Effective Interest Rate Calculator and Explanation
• Effective Interest Rate: Sample Problems and Calculator
• Effective Interest Rate Method: Formula and Example

in p | Loan amount | $ | 20000 | 1 | 100000000
in apr | Interest rate (APR) | % | 8 | 0.01 | 100
in yrs | Loan term | years | 5 | 0.0833 | 50
out pmt | Monthly payment | $ | p * (apr / 1200) / (1 - (1 + apr / 1200) ^ -(yrs * 12)) | 2
out int | Total interest | $ | pmt * yrs * 12 - p | 2