HELOC Calculator

What this HELOC calculator is estimating

A home equity line of credit, or HELOC, is a revolving line secured by home equity. In the United States, lenders often size that line by looking at the home's value, subtracting the existing mortgage balance, and then applying a maximum combined loan-to-value limit. That means the first planning question is not only how much you want to borrow, but whether the requested draw fits inside the line a lender may actually offer.

The second planning question is the payment path. Many HELOCs have an interest-only draw period, which can make the early monthly payment look manageable, followed by a repayment period where the same balance must be paid down over a fixed number of years. Searchers looking for a HELOC payment calculator are usually trying to answer a more practical question than the acronym itself suggests: what will the line look like today, and what happens when the repayment period starts?

This page is explicitly scoped to U.S. home-equity borrowing. It uses HELOC-style combined-LTV screening and repayment framing common in U.S. lending disclosures. It does not attempt to model home-equity rules outside the United States or replace a lender's formal HELOC disclosure package.

How the line and payment estimate works

The worksheet begins with a combined-LTV screen. It multiplies the entered home value by the selected maximum combined loan-to-value percentage, then subtracts the current first-mortgage balance to estimate the line that may be available before any HELOC draw is taken. The requested draw is then compared with that estimated line so you can see whether the request fits and how much undrawn capacity would remain.

During the draw period, the page uses a simplified interest-only assumption on the drawn balance, which means the monthly payment is the balance multiplied by the monthly rate. For the repayment period, it assumes that the same drawn balance converts into a standard amortizing loan at the same fixed rate and spreads repayment over the selected repayment term. That makes the payment shock visible immediately instead of hiding it behind the lower draw-phase number.

This is a deliberate planning simplification. Real HELOCs are often variable-rate products, borrowers can sometimes draw and repay repeatedly during the draw phase, and lenders may apply minimum-payment rules, floors, or different repayment mechanics. The result is therefore best treated as a screening model for the structure of the line rather than a live quote.

Worked example: 400,000 home value, 250,000 mortgage balance, and a 30,000 HELOC draw

Suppose a homeowner estimates the property is worth 400,000, still owes 250,000 on the first mortgage, chooses an 80% combined-LTV screen, plans to draw 30,000, and enters an 8% HELOC rate. Under an 80% CLTV screen, the maximum combined debt would be 320,000, which leaves an estimated 70,000 of line capacity before any HELOC draw. A 30,000 draw would therefore use about 42.86% of that available line and leave about 40,000 undrawn.

At 8%, the simplified draw-period payment on 30,000 is 200 a month if the line is being treated as interest-only. If that same 30,000 balance later converts into a 20-year amortizing repayment term at the same 8% rate, the payment rises to about 250.93 a month. That is the practical reason repayment-phase planning matters: the borrower may experience a payment jump even if the balance itself has not changed.

On this same set of inputs, the combined loan-to-value ratio after the draw is 70%, the draw-period interest cost over a 10-year draw phase would be about 24,000 under the fixed-rate simplification, and the repayment-period interest would add roughly 30,223.68 more if the same balance is then repaid over 20 years. The worksheet is not saying those exact dollars will appear on a future statement. It is showing how line size, rate, and repayment structure interact so you can compare a HELOC with alternatives such as a home equity loan or cash-out refinance.

What this HELOC worksheet does not cover

This page is a planning model, not a lender approval engine. It does not test credit score, debt-to-income ratio, occupancy rules, appraisal adjustments, reserve requirements, lien-position rules, closing costs, annual fees, minimum draw rules, or whether the lender uses a different combined-LTV ceiling than the one you selected here. It also does not model repeated draws and repayments during the draw phase even though many real HELOC borrowers use the line that way.

The other major limitation is rate structure. Many HELOCs have variable rates tied to an index plus a margin, and some also have periodic caps, lifetime caps, introductory rates, or minimum-payment mechanics that differ from this simplified worksheet. Use the page to understand the line-availability logic and the repayment-phase risk, then compare the result with the lender's disclosure, current rate terms, and the actual repayment clause before using the line for a real project or debt strategy.