Mortgage
Monthly payment, interest, and amortization
This Mortgage Calculator estimates the monthly payment on a fixed-rate home loan from three inputs: the loan amount you are financing, the annual interest rate, and the term in years. It also breaks out total interest paid over the life of the loan and provides a year-by-year amortization view.
It is intended for planning and comparison. Real loan offers include other costs (property taxes, insurance, PMI, HOA fees, points, lender fees), so use this number as a baseline and then add those line items separately.
What this calculator estimates
- Monthly principal-and-interest payment for a fully amortizing fixed-rate loan.
- Total interest you will pay across the entire term.
- Total amount paid (principal + interest).
- Amortization breakdown showing how much of each payment goes to interest versus principal over time.
The formula
The standard mortgage payment formula is:
M = P × r × (1 + r)^n / ((1 + r)^n − 1)
Where P is the loan principal, r is the monthly interest rate (annual rate ÷ 12, expressed as a decimal), and n is the number of monthly payments (years × 12). For a zero-interest loan the formula collapses to P / n.
Worked example
Suppose you borrow $300,000 at 6.5% for 30 years.
- Monthly rate:
6.5 / 100 / 12 = 0.005417 - Number of payments:
30 × 12 = 360 - Monthly payment ≈ $1,896
- Total paid over 30 years ≈ $682,633
- Total interest ≈ $382,633 — more than the original principal.
This is why even a small reduction in rate, or making occasional extra principal payments, has an outsized long-term effect.
When this is the right tool
Use it to compare offers (different rate / term combinations), to stress-test affordability before house-hunting, and to see how shortening the term from 30 to 15 years changes total interest paid. For ARMs (adjustable-rate mortgages), this calculator only models the initial fixed-rate behaviour; subsequent rate changes need a more specialised tool.
What this calculator does not include
Property taxes, homeowners insurance, private mortgage insurance (PMI), HOA dues, closing costs, and discount points are all real costs of homeownership that this estimator excludes. Many borrowers find their actual monthly housing payment is 15–30% higher than the principal-and-interest number alone. Always treat lender disclosures as the source of truth.
Frequently asked questions
Does this include taxes and insurance?
No. It calculates only principal and interest. Add your local property tax, homeowners insurance, PMI (if applicable), and HOA fees separately.
How much does the rate really matter?
A great deal. On a $300,000 30-year loan, going from 6.5% to 5.5% saves roughly $200 per month and about $70,000 in interest over the full term.
What about extra principal payments?
Even small extra monthly principal payments shorten the loan and reduce total interest substantially. A dedicated extra-payment calculator is the right tool for modelling that.
Is the amortization schedule accurate?
It applies the standard formula used by US lenders. The actual loan may round to the nearest cent each month, which can cause the final payment to differ by a few cents.