A walkthrough, end to end.
- 1
Enter the home price, down payment, loan term and annual interest rate.
- 2
The calculator solves the standard amortization formula to give your monthly principal-and-interest payment.
- 3
See total interest paid over the loan, plus a year-by-year breakdown of how much of each payment goes to interest vs. principal.
Amortization formula (PMT)
The fixed monthly payment for a fully-amortizing loan is solved from the present-value annuity formula. Each month, interest accrues on the outstanding balance; the rest of your payment reduces principal. Early in the loan, most of the payment goes to interest; late in the loan, most goes to principal.
What you can do with this.
30-year fixed mortgage
The most common US mortgage product. Lowest monthly payment of any standard term, but the most total interest paid. A $400,000 loan at 7% over 30 years pays ~$558K in interest — more than the loan itself.
15-year fixed mortgage
Higher monthly payment but dramatically lower total interest — typically ~60% less than a 30-year on the same loan. Used when income comfortably supports the higher payment and equity-build matters.
Mortgage payment with PMI
If your down payment is under 20%, expect Private Mortgage Insurance of ~0.3–1.5% annually. The calculator's P&I doesn't include PMI, taxes, or insurance — add ~30% for a fully-loaded estimate of PITI.
Home affordability rule of thumb
Lenders typically cap your housing costs (PITI) at 28% of gross monthly income. If the calculated P&I plus your local taxes/insurance exceeds 28%, the loan size is likely too aggressive.
Refinance break-even
Compare your current monthly payment to the new payment after refinancing. Divide closing costs by monthly savings to find the break-even month — anything before you'd sell is a win.
Comparing rates
Even small rate differences compound. A 0.5% lower rate on a $400K, 30-yr loan saves ~$45K total interest. Use the calculator to compare actual quotes side-by-side.
ARM (adjustable-rate) baseline
Adjustable-rate mortgages start lower than fixed but reset after 5–7 years. Compute the worst-case payment at the cap rate to stress-test affordability before committing.
Mortgage calculator 2026 — what's current
30-year fixed rates have hovered in the 6.5–7.2% range through early 2026. Build the calculator into your house-hunt — every quote should be re-checked against your spreadsheet, not just the lender's display.
Frequently asked.
No — only principal and interest (P&I). For total monthly housing cost (PITI), add your local property tax (typically 0.5–2.5% of home value annually divided by 12) and homeowner's insurance.
It depends on the market. Compare your quote to the daily 30-year fixed average from Freddie Mac's PMMS — anything within 0.25% of that is competitive for a borrower with strong credit.
If your rate is above ~5%, extra principal payments save substantial interest. Below ~5%, investing the same money typically beats the savings — depends on your risk tolerance.
Conservative: total housing under 28% of gross monthly income. Stretched: 36%. The calculator helps you check different loan sizes against this rule.
Private Mortgage Insurance, charged when down payment is under 20% on a conventional loan. Typically 0.3–1.5% of the loan annually until you reach 20% equity. Federal loans (FHA) have similar mortgage insurance.
No. Calculations run entirely in your browser. Nothing is sent to a server, no analytics on inputs, no cookies.