How HELOC borrowing capacity is estimated

What this estimate is answering

A simplified HELOC / home equity estimate asks: given a home value, an existing mortgage balance, and an assumed maximum combined loan-to-value (LTV), how much equity and borrowing capacity might a spreadsheet-style formula show?

It does not decide whether a lender will approve a HELOC, set a rate, or underwrite income and credit.

Run the estimate in the HELOC / home equity calculator. For payment and interest tradeoffs on replacing a mortgage, use the mortgage refinance calculator.

The core formulas

Estimated home equity

homeEquity = homeValue − mortgageBalance

If the mortgage is larger than the home value, equity is shown as negative. It is not silently forced to zero.

Assumed maximum secured debt

maximumDebt = homeValue × (maximumLTV ÷ 100)

Estimated available borrowing capacity

estimatedAvailableEquity = maximumDebt − mortgageBalance, then clamped to 0 if that result would be negative.

Current LTV

currentLTV = mortgageBalance ÷ homeValue (shown as a ratio or percent in the UI).

Why maximum LTV is an assumption

Combined LTV limits are not universal. Products and lenders differ. The calculator treats maximum LTV as a number you supply so it does not invent a market rule or “typical” percentage as fact.

Assumptions

• Home value and mortgage balance you enter are treated as accurate for the scenario
• Maximum LTV is an assumption, not a lender quote
• Only the mortgage balance you enter is subtracted; include other liens in that figure if you want them counted
• The MVP does not estimate HELOC interest rates, fees, draw schedules, or payment options
• Approval, credit, income, and property eligibility are out of scope

Limitations

• Not a HELOC approval decision
• Does not invent rates or market averages
• Actual combined LTV and available credit may differ from this simplified estimate

Takeaways

Borrowing capacity here is arithmetic on value, balance, and an LTV assumption. Use it to understand the structure of equity math — not as a promise of what you can borrow.