Utility Calc — Monthly Mortgage Calculator
Utility Calc is a free, privacy-first mortgage education tool that estimates your monthly housing payment and full amortization schedule using the standard banking amortization formula. This page requires JavaScript to run the interactive calculator, but the explanation below describes exactly what it computes so the tool's purpose is clear even without scripting enabled.
What the calculator estimates
The calculator computes your estimated monthly mortgage payment by combining the four components of PITI — Principal, Interest, Taxes, and Insurance — plus optional private mortgage insurance (PMI) when your down payment is below 20%.
- Principal — the portion of each payment that reduces the amount you borrowed (your home price minus your down payment).
- Interest — the cost of borrowing, charged each month on the remaining balance. Because the balance is highest at the start, interest dominates the early years and principal dominates the later years.
- Property taxes — your annual local tax bill, divided by 12 and collected through an escrow account.
- Homeowners insurance — your annual premium, divided by 12 and collected through escrow.
- PMI — an estimated charge applied only when your down payment is under 20%, until you reach that equity threshold.
The monthly principal-and-interest payment is calculated with the standard amortization formula: M = P × [r(1 + r)n] / [(1 + r)n − 1], where M is the monthly payment, P is the loan amount, r is the monthly interest rate (annual rate divided by 12), and n is the total number of monthly payments (term in years times 12). The tool also shows total interest paid, payoff time, and a year-by-year amortization schedule, and it can model how extra monthly principal payments shorten the loan and reduce interest.
Disclaimer: All calculations are automated estimates intended for educational planning purposes only. Actual interest rates, loan terms, and monthly payments are determined exclusively by individual lending institutions, and the results depend entirely on the assumptions you enter. These estimates do not guarantee loan qualification and do not constitute financial, investment, legal, or lending advice. Consult a licensed mortgage broker or certified financial professional before making any financial commitments.
To use the interactive calculator, please enable JavaScript in your browser. No data you enter is sent to any server — every calculation runs locally in your browser.