HELOC Calculator
Find out how much you can borrow against your home equity. Enter your home value, mortgage balance, and draw amount to see your maximum HELOC, monthly payments, and total interest.
HELOC Explained: How a Home Equity Line of Credit Works
A Home Equity Line of Credit, commonly known as a HELOC, is a revolving credit facility secured by the equity in your home. Unlike a traditional home equity loan that provides a single lump sum, a HELOC works more like a credit card: you draw funds as needed up to a set limit during a draw period, then repay what you borrowed during a repayment period. Understanding how HELOCs are calculated helps you plan borrowing, manage cash flow, and compare costs before committing.
How Your HELOC Limit Is Determined
Lenders determine your maximum HELOC amount by applying a loan-to-value (LTV) ratio to your home's appraised value, then subtracting your existing mortgage balance. The formula is: Max HELOC = (Home Value x Max LTV%) minus Mortgage Balance. Most lenders cap the combined LTV (your mortgage plus the HELOC) at 80%, though some may extend to 85% or 90% for well-qualified borrowers.
For example, if your home is worth $400,000, you owe $200,000 on your mortgage, and the lender's max combined LTV is 80%, your maximum HELOC would be ($400,000 x 0.80) minus $200,000 = $120,000. Your actual available credit may be lower depending on your credit score, income, and the lender's policies.
Draw Period vs. Repayment Period
A HELOC typically has two phases. During the draw period, commonly 5 to 10 years, you can borrow from the line, repay it, and borrow again. Many lenders require interest-only payments during this phase, which keeps monthly costs low but does not reduce the principal balance.
Once the draw period ends, you enter the repayment period, usually 10 to 20 years. During this phase you can no longer draw funds and must repay the remaining balance through regular principal-and-interest payments. The payment often increases significantly at this transition, sometimes referred to as payment shock, so planning ahead is essential.
Interest-Only vs. Principal and Interest Payments
During the draw period, lenders typically require only interest payments on the outstanding balance. The monthly interest-only payment is: Interest Payment = Balance x (Annual Rate / 12). This payment fluctuates as your balance and the interest rate change, since most HELOCs carry a variable rate tied to the prime rate.
The principal-and-interest (P+I) payment for the repayment period uses the standard amortization formula: M = P x [r(1+r)^n] / [(1+r)^n - 1], where P is the draw amount, r is the monthly interest rate, and n is the number of repayment months. This payment is fixed for the repayment term if the rate is locked, or recalculates periodically for variable-rate HELOCs.
Variable Interest Rates and Rate Risk
Most HELOCs carry a variable interest rate, typically indexed to the Wall Street Journal Prime Rate plus a margin. This means your payment can rise or fall as the benchmark rate changes. When central banks raise rates, HELOC rates follow quickly, increasing both the interest-only and eventual P+I payments.
Some lenders offer the ability to convert a portion of the outstanding balance to a fixed-rate sub-account, providing payment certainty on that portion. When evaluating a HELOC, consider how higher rates would affect your payments. A HELOC at 8% on a $100,000 draw carries an interest-only payment of about $667 per month; if the rate rises to 10%, the payment becomes $833, a 25% increase with no change in balance.
Total Interest Cost
The total interest paid over the repayment period depends on the draw amount, interest rate, and repayment term. Longer repayment terms lower monthly payments but increase total interest. For a $100,000 draw at 8% over 10 years, total interest is roughly $44,000; over 15 years at the same rate, it rises to about $69,000.
Making extra payments during the repayment period, or even during the draw period, directly reduces the principal and cuts total interest. Most HELOCs allow prepayment without penalties, making them flexible if your financial situation improves. Always confirm this with your lender before drawing funds.
Common Uses and Considerations
HELOCs are commonly used for home improvements (which may preserve or enhance the home's value), debt consolidation, education expenses, and other large planned costs. Because the credit line is secured by your home, interest rates are typically lower than unsecured alternatives like personal loans or credit cards.
However, because your home serves as collateral, failure to repay a HELOC can result in foreclosure. Borrowers should ensure the debt level remains manageable and that they have a clear plan for repayment before the draw period ends. This calculator provides estimates based on the inputs you provide. Consult a financial advisor or lender for personalized guidance before proceeding.
Frequently Asked Questions
What is a HELOC and how does it differ from a home equity loan?
A HELOC is a revolving line of credit secured by your home equity, similar to a credit card: you draw funds as needed up to a limit and repay over time. A home equity loan (also called a second mortgage) provides a lump sum upfront with fixed monthly payments from day one. HELOCs typically have variable rates and flexible access, while home equity loans offer rate and payment certainty.
How much equity do I need to qualify for a HELOC?
Most lenders require at least 15% to 20% equity in your home after accounting for both your first mortgage and the HELOC. In practice, this means your combined loan-to-value ratio (mortgage + HELOC divided by home value) must not exceed 80% to 85%. Lenders also consider your credit score, debt-to-income ratio, and employment history when determining eligibility and the credit limit.
What happens at the end of the draw period?
When the draw period ends, you can no longer access funds from the line. The outstanding balance transitions to the repayment period, where you make fixed principal-and-interest payments until the balance is paid off. Some lenders require a balloon payment at the end of the draw period, while others allow refinancing the balance into a new loan. Review your HELOC agreement carefully to understand the end-of-draw terms.
Is HELOC interest tax deductible?
Under current U.S. tax law, interest on a HELOC may be deductible if the funds are used to buy, build, or substantially improve the home securing the loan, subject to the $750,000 combined mortgage debt limit for interest deductions. Interest used for other purposes, such as paying off credit cards or funding vacations, is generally not deductible. Tax rules change over time, so consult a tax professional for advice specific to your situation.
Can I pay off a HELOC early?
Most HELOCs allow early repayment without prepayment penalties. Some lenders charge an early closure fee if the line is closed within the first 2 to 3 years. Making extra payments reduces your balance, lowers your interest charges, and can shorten the effective repayment period. During the draw period, you can repay and re-borrow, giving you flexible access to capital as your needs evolve.