Monthly mortgage payments are calculated using the standard amortization formula:
Monthly Payment = P × r(1+r)^n ÷ [(1+r)^n − 1]
Where P = loan amount, r = monthly interest rate, n = total number of payments
No need to do the math manually — use tool.tl's mortgage calculator to get your monthly payment, total interest, and full amortization schedule instantly.
Loan amount = Home price minus down payment. A larger down payment means a smaller loan, lower monthly payments, and less total interest. On a $400,000 home:
Rate has the biggest impact on total cost. Example: $300,000 loan, 30-year term:
| Rate | Monthly Payment | Total Interest (30 yr) |
|---|---|---|
| 5.5% | $1,703 | $313,212 |
| 6.5% | $1,896 | $382,633 |
| 7.0% | $1,996 | $418,527 |
| 7.5% | $2,098 | $455,367 |
Longer terms mean lower monthly payments but significantly more total interest:
| Term | Monthly Payment ($300K, 6.5%) | Total Interest |
|---|---|---|
| 10 years | $3,394 | $107,243 |
| 15 years | $2,614 | $170,587 |
| 30 years | $1,896 | $382,633 |
Extra payments go directly toward principal, dramatically reducing total interest. On a $300,000, 6.5%, 30-year mortgage:
Use tool.tl's mortgage calculator to model your own extra payment scenarios.
Yes — tool.tl's mortgage calculator is completely free, no account required, and all calculations happen locally in your browser.
The base calculator focuses on principal and interest (P&I). Your actual monthly payment (PITI) will also include property taxes and homeowner's insurance — typically 1–2% of home value annually, divided across 12 months.
The interest rate is the base cost of borrowing. APR (Annual Percentage Rate) includes the interest rate plus fees (origination fees, mortgage points, etc.), giving a more complete picture of the true loan cost. Always compare APRs when shopping for mortgages.