HELOC Calculator
Estimate how large a home equity line of credit you could qualify for, then see what monthly payments look like in both the draw and repayment phases. Free, no sign-up, runs entirely in your browser.
CLTV is your mortgage plus HELOC divided by home value. Many lenders cap it at 80%, some allow 85% or 90% with strong credit.
Estimate only. Lenders also underwrite credit score, income and debt-to-income ratio, and may approve less.
Assumes the full balance is drawn for the entire draw period at a constant rate. Most HELOC rates are variable, so real payments will move with the prime rate.
How the HELOC math works
Borrowing power. Lenders limit your combined loan-to-value ratio: your existing mortgage plus the new HELOC, divided by your home's appraised value. The maximum line is home value × CLTV cap − mortgage balance, floored at zero. On a $500,000 home with a $300,000 mortgage, an 80% cap yields $100,000, an 85% cap yields $125,000, and a 90% cap yields $150,000.
Draw period payments. During the draw period most HELOCs require interest-only payments: balance × rate ÷ 12. A $50,000 balance at 8% costs about $333.33 per month. Because the rate is usually variable, this payment changes whenever your lender's index (typically the prime rate) changes.
Repayment period payments. Once the draw period ends, the balance amortizes like a standard installment loan using P × r ÷ (1 − (1 + r)−n), where r is the monthly rate and n is the number of months. The same $50,000 at 8% repaid over 20 years costs about $418.22 per month, so budget for the payment jump when the draw period ends.
Worked example
| Item | Amount |
|---|---|
| Home value | $500,000 |
| Mortgage balance | $300,000 |
| Max line at 80% CLTV | $100,000 |
| Interest-only payment on $50,000 drawn at 8% | $333.33/mo |
| Repayment payment over 20 years at 8% | $418.22/mo |
Frequently asked questions
What is a HELOC?
A home equity line of credit is a revolving line of credit secured by your home. You draw and repay as needed during the draw period (often 5 to 10 years), usually paying interest only on what you have drawn, then repay principal plus interest over the repayment period (often 10 to 20 years).
What is the difference between a HELOC and a home equity loan?
A home equity loan is a single lump sum at a fixed rate with fixed payments from day one. A HELOC is a reusable credit line, usually with a variable rate and interest-only payments while you draw. Choose a HELOC for ongoing or uncertain costs, a home equity loan for one known expense and predictable payments.
How much can I borrow with a HELOC?
Roughly home value × CLTV cap (80% to 90%) minus your mortgage balance. A $500,000 home with a $300,000 mortgage supports up to $100,000 at an 80% cap or $150,000 at a 90% cap. Credit score, income and debt-to-income ratio also apply, so the approved line can be lower.
Are HELOC rates variable?
Usually. Most HELOCs price at the prime rate plus a margin, so payments rise and fall with the prime rate. Some lenders offer fixed-rate locks on portions of the balance. Always test a rate 1 to 2 points above today's when planning your budget.