Mortgage Interest Calculator for Payments and Total Interest
Calculate monthly principal and interest, total mortgage interest, taxes, insurance, and full housing cost for a home loan.
Enter home price, down payment, rate, term, annual tax, and annual insurance to separate the interest cost of financing from escrow items.
Mortgage Interest Calculator for Payments and Total Interest
Calculate monthly principal and interest, total mortgage interest, taxes, insurance, and full housing cost for a home loan.
About the Mortgage Interest Calculator
The mortgage interest calculator highlights how much a fixed-rate home loan costs in interest, while still showing the monthly housing payment that includes tax and insurance. Buyers who have already seen a payment quote often still ask how much of that money is interest versus principal. Enter home price, down payment, annual rate, term, annual property tax, and annual homeowners insurance. Principal is price minus down payment. The primary result is the combined monthly total; total interest is the supporting figure that answers the financing-cost question.
Principal and interest use the standard amortization formula with monthly rate i = r/12. Total interest assumes the scheduled P&I payment is made for every month of the term: payment × n − principal. That identity is exact for a fixed payment with no extra principal. Property tax and insurance are converted to monthly escrow amounts and added to P&I for the monthly total. They are not part of total interest, because they are ownership costs rather than lender interest.
Use the mortgage interest calculator to compare a higher rate with a shorter term, to see how a larger down payment cuts lifetime interest, and to explain why two loans with similar payments can have very different interest totals. A 15-year loan often has a similar PITI to a 30-year loan on a smaller principal, yet it can save six figures of interest. PMI and HOA dues are omitted; add them separately or use the taxes-and-insurance mortgage calculator.
Actual interest falls if you sell, refinance, or prepay. Deductibility of mortgage interest depends on tax law and is not estimated here. Lender quotes may round the payment to the nearest cent using a slightly different day-count. Recalculate after a rate lock change, and keep tax and insurance as annual figures so the interest comparison stays focused on the note rate and term.
Mortgage Interest Calculator Examples
These worked examples use the same payment and total-interest formulas as the mortgage interest calculator.
| Inputs | Result | Why it matters |
|---|---|---|
| $400,000 price, $80,000 down, 6.5% rate, 30 years, $4,800 tax, $1,800 insurance | Monthly total $2,572.62; P&I $2,022.62; total interest $408,142.36 | Interest over 30 years exceeds the $320,000 principal on this 6.5% loan. |
| $350,000 price, $70,000 down, 6% rate, 20 years, $3,600 tax, $1,200 insurance | Monthly total $2,406.01; P&I $2,006.01; total interest $201,441.67 | Cutting the term to 20 years roughly halves lifetime interest versus a typical 30-year path. |
| $500,000 price, $50,000 down, 7% rate, 30 years, $6,000 tax, $2,000 insurance | Monthly total $3,660.53; P&I $2,993.86; total interest $627,790.04 | A smaller down payment and higher rate push total interest well above the amount borrowed. |
How to Use the Mortgage Interest Calculator
- Enter home price and down payment to set the loan principal.
- Enter the annual rate, term in years, annual property tax, and annual homeowners insurance.
- Select Calculate to view principal and interest, monthly escrow items, monthly total, and total interest.
- Change the term or down payment to see how lifetime interest moves relative to the monthly total.
Mortgage Interest Calculator FAQ
What does total interest include?
Total interest is the scheduled principal-and-interest cost minus the original principal. It does not include property tax, homeowners insurance, PMI, or HOA dues.
Why show tax and insurance on an interest calculator?
Most buyers budget a full monthly housing payment, not P&I alone. Tax and insurance are shown so the interest figure can be read next to a realistic monthly total.
Does extra principal change total interest?
In this estimate, no extras are applied, so total interest is the full-term amount. Extra principal would reduce actual interest; use the mortgage amortization calculator to model that path.
Is mortgage interest tax-deductible?
Sometimes, depending on the loan, filing status, and current tax rules. The mortgage interest calculator does not estimate a tax deduction or after-tax cost.
How is principal calculated?
Principal is home price minus down payment. Entering an already-netted loan amount in the price field and a down payment would shrink principal twice.