Flagstone Digital

HELOC calculator: credit line and payments

Estimate how large a home equity line of credit you might get, and what payments could look like during the draw and repayment periods.

Free · No sign-up · Updated October 2026

HELOC calculator

Estimated maximum credit line$0
Interest-only payment during draw period
Payment once repayment begins
Change when repayment begins

Example rate shown; HELOC rates are usually variable and change over time. Payments assume the rate stays the same.

Want to compare real HELOC offers? A licensed mortgage loan officer can give you real rates and terms. It's free and there's no obligation.

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How a HELOC works

A home equity line of credit (HELOC) is a revolving line of credit secured by your home. It usually sits on top of your existing mortgage as a second lien, so your current mortgage and its rate stay the same.

Most HELOCs have two phases:

  1. Draw period, often around 10 years. You can borrow, repay and borrow again up to your limit. Many HELOCs let you pay only interest during this time.
  2. Repayment period, often 10 to 20 years. You can no longer draw, and payments include principal, so they usually go up.

The CFPB's guide to home equity loans and HELOCs explains the difference between the two in more detail.

How your credit line is calculated

Lenders typically cap your combined loan-to-value (CLTV), meaning your mortgage plus the HELOC, at around 80% to 90% of your home's value.

Example at 85%$650,000 × 85% = $552,500$552,500 − $310,000 mortgage = about $242,500 maximum line

Watch for these

  • Variable rates. Most HELOC rates are tied to an index such as the prime rate, so your payment can change.
  • Payment jump. Moving from interest-only to principal-and-interest payments can raise your payment significantly. The calculator above shows the difference.
  • Fees. Ask about closing costs, annual fees, minimum draw requirements and early closure fees.
  • Your home is collateral. Missing payments can put your home at risk.

HELOC or cash-out refinance?

A HELOC keeps your current mortgage in place, which can matter if your existing rate is lower than today's rates. A cash-out refinance replaces your whole mortgage with one new loan and one rate. Comparing both side by side is often worthwhile.

Frequently asked questions

Is a HELOC rate fixed or variable?

Most HELOC rates are variable and move with an index such as the prime rate. Some lenders offer an option to lock part of your balance at a fixed rate.

Can I pay only interest on a HELOC?

Many HELOCs allow interest-only payments during the draw period. Once repayment begins, payments include principal and usually increase.

Does a HELOC replace my mortgage?

No. A HELOC is usually a separate second loan. Your existing mortgage and its rate stay the same.

How long is a HELOC draw period?

It varies by lender, but around 10 years is common, followed by a repayment period of 10 to 20 years.

How much can I get with a HELOC?

Lenders typically allow your mortgage plus the HELOC to total 80% to 90% of your home's value, depending on credit, income and the property.

About this calculator

This calculator uses standard loan formulas and the numbers you enter. It runs in your browser, doesn't check your credit and doesn't save anything unless you choose to request options. Results are estimates for education only. Lenders set their own limits, rates and fees.

For independent guidance, see the Consumer Financial Protection Bureau's homebuying resources.