نظرة عامة
Mortgage & Refinance Calculator
A free, bilingual application for planning mortgage payments, exploring home affordability, and comparing refinance options.
Mortgage & Refinance Calculator helps users understand potential housing costs through clear inputs, visual breakdowns, and side-by-side comparisons. Users can enter their own financial details or explore explicitly labeled examples.
Developed by PandaDev, the application requires no account and performs its financial calculations directly in the browser. Three Focused Calculators The introductory homepage provides three cards, each linking to a dedicated calculator page. Mortgage Calculator Estimate a regular monthly housing payment using:
- Home price.
- Down payment, entered in dollars or percent.
- Annual interest rate.
- Loan terms of 10, 15, 20, 25, 30, or 40 years.
- Optional annual property taxes and home insurance.
- Optional monthly homeowners association fees.
- Configurable private mortgage insurance assumptions. Results include a monthly payment estimate, an itemized cost breakdown, and a donut chart showing how the entered costs contribute to the total.
Missing optional costs are identified so users can distinguish an incomplete estimate from an explicitly entered zero. Home Affordability Calculator Explore an estimated home price limit based on:
- Annual income before taxes.
- Existing monthly debt payments.
- Available down payment.
- Interest rate and loan term.
- Optional property taxes, insurance, and HOA fees.
- Editable housing and total debt-to-income guidelines. Results show the estimated home price limit, loan amount, monthly housing budget, and a chart comparing income, housing capacity, and existing debt payments.
The result is a planning guideline, not lender approval or prequalification. Refinance Calculator Compare an existing mortgage with a proposed new loan using:
- Remaining loan balance.
- Current interest rate and years remaining.
- New interest rate and loan term.
- Closing costs.
- An option to finance closing costs into the new loan. Results include current and proposed principal-and-interest payments, estimated monthly savings or increases, remaining payment differences, and a simplified cash break-even estimate where applicable. Extra Payment Planning The mortgage calculator supports additional contributions made:
- Every month.
- Every year.
- Once, at a selected payment number. Users can explore estimated interest savings, reduced repayment time, and the monthly total including recurring extra payments.
A visible payoff graph compares the remaining loan balance under regular payments with the balance when extra payments are included. Amortization Schedule and Exports An expandable payment schedule shows how payments are divided between principal and interest.
Users can:
- Switch between yearly summaries and monthly details.
- Review the remaining loan balance.
- Download the monthly schedule as a CSV file.
- Print results or save them as a PDF through the browser’s print dialog. Taxes, insurance, HOA fees, and PMI are excluded from the principal-and-interest amortization schedule. English and Spanish A language selector is available throughout the application.
English and Spanish support includes:
- Page headings and navigation.
- Input labels and explanations.
- Validation messages.
- Calculation results and notices.
- Chart labels and footer content. The language preference is stored separately from financial inputs. All monetary amounts remain in US dollars (USD); changing the language does not convert currency or change calculation assumptions. User-Friendly Design The application uses one consistent theme combining navy framing, light content surfaces, and blue/aqua accents.
Its interface includes:
- Larger text and readable input values.
- Aligned desktop inputs and stacked mobile fields.
- Separate pages for each calculator.
- Expandable sections for secondary settings.
- Clear empty states before required information is entered.
- Labeled sample scenarios.
- Keyboard focus indicators and a skip-to-content link.
- Responsive layouts checked at widths down to 320 pixels. The application name appears in the header, with the original PandaDev logo and attribution in the footer. Privacy and Local Storage Financial calculations run locally in the browser.
Financial inputs remain in memory unless the user enables Remember my inputs on this device. When enabled, inputs are saved in that browser’s local storage.
Users can:
- Clear the active calculator.
- Start over to clear all calculator inputs and disable financial saving.
- Continue using the calculators when browser storage is unavailable. Local storage is not encrypted. Users should leave financial saving disabled on shared devices.
The current application does not include an analytics integration, a visitor activity database, an administrator account, or a monitoring dashboard. Security The application is designed to operate without server credentials or sensitive configuration in browser code.
Security measures include:
- Input validation and bounded calculation ranges.
- Validation of restored financial data.
- A maximum amortization calculation length of 600 payments.
- CSV escaping and spreadsheet formula-prefix protection.
- Same-origin application assets and system fonts.
- A strict Content Security Policy in the Render configuration.
- Framing protection, content-type protection, and restricted browser permissions.
- Localhost-only development and preview servers. These controls reduce risk but do not constitute a guarantee against all vulnerabilities. Technology and Hosting Component Technology Interface React Build system Vite Application code JavaScript and JSX Styling CSS Icons Lucide React Financial calculations Pure JavaScript functions Optional local persistence Browser localStorage Calculation tests Node.js test runner Browser tests Playwright with Microsoft Edge Deployment target Render Static Site
The application requires no backend, database, API keys, or persistent server disk.
The repository includes a Render Blueprint that builds the application, publishes the dist directory, configures security headers, and supports direct visits to calculator URLs. Application Pages URL Purpose / Introduction and calculator selection /mortgage Mortgage payments, extra payments, and amortization /affordability Home affordability estimation /refinance Current and proposed mortgage comparison
Calculation Assumptions and Limitations
- Results are educational estimates, not financial advice, loan offers, or prequalification.
- Missing optional expenses are excluded and identified.
- Taxes and insurance are entered annually; HOA fees are entered monthly.
- Automatic PMI assumes a conventional loan with less than 20% down. Users can override whether PMI is included.
- PMI remains fixed in the model. Cancellation rules and FHA/VA mortgage insurance are not modeled.
- Annual extra payments apply every 12th payment.
- Calendar payoff dates require a first payment date; otherwise, payoff is expressed as a payment count.
- Affordability excludes PMI, closing costs, and some lender-specific requirements.
- Refinance cash break-even uses upfront closing costs divided by monthly principal-and-interest savings.
- Cash break-even is not calculated for financed closing costs or shown beyond the compared payment horizon.
- Tax effects, opportunity costs, and differences in equity over time are excluded from refinance comparisons.