Home Equity Line of Credit (HELOC) Calculator

How a Home Equity Line of Credit Works

A home equity line of credit (HELOC) lets homeowners borrow against the equity in their property as a revolving credit line. Unlike a home equity loan that provides a lump sum, a HELOC works more like a credit card where you draw funds as needed up to a maximum limit. The borrowing limit is based on your home's value, your existing mortgage balance, and the lender's maximum combined loan-to-value ratio, typically 80 to 85 percent.

HELOCs have two phases. During the draw period, usually 5 to 10 years, you can borrow and repay funds as needed while making interest-only minimum payments. When the draw period ends, the repayment period begins, typically lasting 10 to 20 years. During repayment, you can no longer borrow against the line and must make full principal and interest payments on the outstanding balance. The shift from interest-only to P&I payments can significantly increase your monthly obligation.

Understanding Combined Loan-to-Value

Combined loan-to-value (CLTV) is the total of all loans secured by your property divided by the home's current market value. If your home is worth $400,000 and you owe $250,000 on your mortgage, your current LTV is 62.5%. If you add a $50,000 HELOC draw, your combined LTV becomes 75%. Most lenders cap CLTV at 80%, though some allow up to 85% or 90% with higher rates.

The maximum HELOC amount is calculated as the home value multiplied by the maximum CLTV percentage, minus your existing mortgage balance. On a $400,000 home with an 80% CLTV cap and $250,000 mortgage, the maximum HELOC is $70,000. This calculator shows both the maximum available and the combined LTV after your planned draw, so you can see exactly where you stand relative to lender limits.

Interest-Only vs. Principal and Interest Payments

During the draw period, most HELOCs require only interest payments on the outstanding balance. On a $50,000 draw at 8.5%, the monthly interest-only payment is roughly $354. This makes the draw period affordable, but no principal is being repaid. The full balance remains outstanding when the repayment period begins.

When the repayment period starts, the payment converts to a fully amortizing principal and interest schedule. On the same $50,000 at 8.5% over 20 years, the monthly payment jumps to approximately $434. This payment shock catches many borrowers off guard. This calculator shows both payment amounts and the dollar increase so you can plan for the transition.

Why HELOC Rate Sensitivity Matters

Most HELOCs carry variable interest rates tied to the prime rate, which moves with the Federal Reserve's benchmark rate. When rates rise, your HELOC payment increases immediately during the draw period and affects the payment calculation when the repayment period begins. A 2% rate increase on a $50,000 balance adds roughly $83 per month to the interest-only payment.

The rate sensitivity section of this calculator shows what your payments would look like if rates increased by a specified amount. This is important for budgeting because HELOC rates can move significantly over a 10-year draw period. Borrowers should stress-test their ability to handle higher payments before committing to a HELOC, especially for amounts that represent a large portion of their available equity.

Using a HELOC for Real Estate Investment

Real estate investors commonly use HELOCs on their primary residence or existing investment properties to fund down payments, rehab costs, or bridge financing for new acquisitions. The interest-only draw period keeps carrying costs low while the investor deploys the capital, and the line can be repaid and reused after each project.

The key risk is that the HELOC is secured by your property. If an investment deal goes wrong and you cannot repay the line, your home is at risk. Investors should calculate the total cost of borrowing, including all interest paid during both the draw and repayment periods, and compare that cost against the expected return on the investment being funded. This calculator shows total interest as both a dollar amount and a percentage of the amount borrowed to help evaluate whether the cost of capital makes sense for the intended use.

Frequently Asked Questions

How much can I borrow with a HELOC?

The maximum is your home value multiplied by the lender's CLTV limit (typically 80-85%), minus your mortgage balance. On a $400,000 home with 80% CLTV and a $250,000 mortgage, the max HELOC is $70,000.

What is the difference between the draw period and repayment period?

During the draw period (typically 5-10 years), you borrow as needed and make interest-only payments. During the repayment period (10-20 years), borrowing stops and you make full principal and interest payments on the outstanding balance.

Are HELOC rates fixed or variable?

Most HELOCs have variable rates tied to the prime rate. When the Federal Reserve raises or lowers rates, your HELOC rate and payment adjust accordingly. Some lenders offer fixed-rate lock options for portions of the balance.

How much does a rate increase affect my payment?

Each 1% rate increase adds approximately the draw amount divided by 1,200 to your monthly interest-only payment. On a $50,000 balance, a 1% increase adds roughly $42 per month. Use the rate sensitivity section to model specific scenarios.

Can I use a HELOC for a rental property down payment?

Yes, many investors use HELOCs on their primary residence to fund investment property purchases. The interest-only payments keep carrying costs low during the acquisition and rehab phase. However, the HELOC is secured by your home, so evaluate the risk carefully.

What happens if my home value drops?

If your home value decreases, your equity shrinks and the lender may reduce or freeze your credit line. In severe cases, the combined LTV could exceed 100%, putting you in a negative equity position on the HELOC portion. Monitor your home value relative to your total debt.