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 (HELOC) is a revolving line of credit secured by your home. During the draw period, often 5 to 10 years, you can borrow and repay as needed and usually pay interest only on the amount drawn. After the draw period ends, the repayment period begins, typically 10 to 20 years, during which you can no longer draw and must repay principal plus interest.
What is the difference between a HELOC and a home equity loan?
A home equity loan pays you one lump sum at a fixed interest rate with fixed monthly payments from day one. A HELOC is a revolving credit line you draw from as needed, usually at a variable rate, with interest-only payments during the draw period. A HELOC suits ongoing or uncertain expenses; a home equity loan suits a single known cost and payment stability.
How much can I borrow with a HELOC?
Most lenders cap your combined loan-to-value ratio (CLTV) at 80% to 90% of your home's appraised value. Your maximum credit line is roughly your home value times the CLTV cap, minus your current mortgage balance. For example, a $500,000 home with a $300,000 mortgage at an 85% cap allows up to $125,000. Lenders also consider credit score, income and debt-to-income ratio, and the final line can be lower.
Are HELOC rates variable?
Usually, yes. Most HELOCs carry a variable rate tied to the prime rate plus a margin, so your rate and your interest-only payment change whenever the prime rate moves. Some lenders let you lock portions of the balance at a fixed rate. When modeling payments, test a higher rate than today's to see how a rate increase would affect your budget.