How to use the HELOC calculator
- Enter your home's value and what you owe on the mortgage, then the combined loan-to-value (CLTV) limit your lender uses. 80% to 85% is common, and some lenders go to 90%. The large figure is the most you could borrow at that limit.
- Enter the amount you want to borrow and the rate. A HELOC's rate is the prime rate plus the lender's margin, both in your offer. Set the draw period (often 10 years), the repayment period (often 20) and whether the draw period payments cover interest only.
- Read the two payments and the payment shock. The draw period payment is what you pay while you can still borrow; the repayment payment is what you pay once the line closes and the balance must be repaid.
- Stress-test the rate with the scenarios, and compare with a home equity loan and a cash-out refinance under the results.
No sign-up, no email and no lead form: everything runs in your browser, and nothing you type is sent anywhere. Share result saves the inputs in the link itself, and the schedule downloads as CSV for a spreadsheet.
How much can you borrow?
Lenders start from the combined loan-to-value: everything secured on the home divided by its value. Borrowing power = home value × max CLTV − mortgage balance. On a 400,000 home with 220,000 owed and an 85% limit, that is 340,000 − 220,000 = 120,000. Approval then depends on your credit score, income and debt-to-income ratio, and on an appraisal of the home, so the real limit can be lower.
In Canada, federally regulated lenders follow OSFI's Guideline B-20: the revolving line of credit is limited to 65% of the home's value, and a HELOC combined with an amortizing mortgage to 80%. Pick Canada under Lending rules to apply both limits.
Draw period, repayment and payment shock
During the draw period you can borrow, repay and borrow again, and most HELOCs require only the interest: balance × rate ÷ 12. When it ends, the line closes and the balance is repaid in level monthly payments over the repayment period: P × i ÷ (1 − (1 + i)^−n), where i is the monthly rate and n the number of months. Because principal is added and the time to repay is shorter than the whole term, the payment jumps. For 50,000 at 8%, it goes from 333.33 to 418.22 a month, a 25% rise. A shorter repayment period, a higher rate or a balloon payment makes the jump bigger.
To soften it, pay principal during the draw period: set Draw period payments to principal and interest, or add an extra monthly payment and watch the balance owed when repayment starts fall.
If rates rise
Most HELOC rates follow the prime rate, which moves with the Federal Reserve's federal funds rate. The US prime rate was 7.00% on September 21, 2026. The scenario table moves your rate by −1 to +3 percentage points for the whole life of the line, up to the lifetime cap in your agreement, and shows what each does to both payments and the total interest. Some lenders let you lock part of the balance at a fixed rate, which is worth asking about if a rise would strain your budget.
HELOC vs home equity loan vs cash-out refinance
All three turn home equity into cash. The comparison includes your current mortgage, so each row covers everything you'd owe:
- HELOC: keep your mortgage and add a variable-rate line. The lowest payment at first, but the payment jumps later and follows rates.
- Home equity loan: keep your mortgage and add a fixed-rate lump sum with the same payment from the first month.
- Cash-out refinance: replace the mortgage with a bigger one at today's rate, with closing costs financed into it. The 30-year average was 7.03% for the week of September 24, 2026 (Freddie Mac).
If your mortgage rate is well below today's rates, keeping it usually wins: the blended rate of the mortgage and a HELOC is much lower than refinancing everything. A cash-out refinance can make sense when your current rate is already close to today's, or when one fixed payment matters more than the total cost. If you could use savings instead of borrowing, the interest calculator shows what that money would earn if you left it where it is.
Your home secures a HELOC: if you can't pay, you could lose it. Plan for the repayment payment, not only the first one. Mark the date the draw period ends on a printable calendar, and line payments up with your paydays using the pay period calendar.
Sources, checked September 2026: Board of Governors of the Federal Reserve System, H.15 bank prime loan rate via FRED (DPRIME), September 21, 2026; Freddie Mac Primary Mortgage Market Survey via FRED (MORTGAGE30US); CFPB, What you should know about home equity lines of credit; OSFI, Guideline B-20. For planning, not financial advice.