Home Equity Line Payment Calculator Overlay

WHAT IT DOES

This userscript helps homeowners understand HELOC payment obligations by projecting payments across draw and repayment periods. It scans home equity loan or HELOC pages, bank websites, or financial calculators for loan details—credit limit, outstanding balance, interest rate, draw period, repayment period, and current payment. It displays an interactive calculator panel to project payments and costs, extract figures from text, calculate monthly payments during draw and repayment periods, show total interest costs, and display a payment timeline. The script compares different repayment strategies, shows the impact of rate changes, highlights the cheapest repayment option, and exports the analysis as CSV or HTML. It suggests accelerated payment strategies to reduce interest costs.

WHERE IT RUNS

The script works on home equity loan pages, HELOC pages, bank websites, and any page with loan data. It runs entirely within your browser, reading only the visible content of the current page. It does not track your browsing history, access other tabs, or send any data externally. All HELOC data is processed and stored locally.

HOW TO USE

After installation, open the panel by clicking the tool's icon in the BotGentz sidebar. Enter your credit limit, outstanding balance, interest rate, draw period (years), repayment period (years), current payment, and any extra payment. Click "Calculate HELOC Payments" to see draw payment, repayment payment, total interest, and total months. A payment timeline bar chart shows the balance progression through draw and repayment periods. Use "Extract from page" to auto-fill HELOC data from the current page. Use the export dropdown to choose your format—CSV or HTML (report). Click "Export" to download.

THE TECHNICAL MECHANISM

This script uses two-phase loan amortization for HELOC calculations. During the draw period, payments are interest-only: payment = balance × monthly rate. During the repayment period, payments are fully amortizing using the formula: P = principal × (r(1+r)^n) / ((1+r)^n - 1), where r is the monthly interest rate and n is the number of months. The projection runs month-by-month, tracking interest, total paid, and remaining balance for each year. The draw period keeps the balance constant while interest accrues. The repayment period reduces the balance until it reaches zero. The timeline chart shows the balance progression with color coding (blue for draw, green for repayment). The export generates CSV or HTML with all metrics. All data is persisted using GM_setValue.

THE PANEL

The panel is draggable anywhere on the screen and remembers its position between sessions. It can be collapsed to a small floating bubble to minimize distraction, and expanded again with a single click. The panel's width can be adjusted, and pressing the Escape key closes it instantly. All settings and HELOC data are persisted locally using GM_setValue, so your calculations remain intact across page reloads and browser restarts.

PLEASE NOTE

This userscript requires the free BotGentz extension to function. The script extracts figures from page text—it may not capture all numbers correctly. Review and adjust extracted data as needed. The calculations are estimates based on the data provided and do not account for all loan fees or rate changes. The script does not access external APIs or store any data outside your browser. No data from your browsing is stored or transmitted anywhere—all processing occurs entirely in your browser.