HELOC Calculator

How to Use This HELOC Calculator

A HELOC feels manageable during the draw period—interest-only payments on a $50,000 balance might look like a car note. Then the repayment phase hits and your payment can jump overnight because principal finally enters the picture. If you are planning a renovation or comparing a HELOC to a fixed home equity loan, run both phases here first so the later bill does not catch you off guard.

• Enter the loan amount. Use the balance you expect to draw fully—or the credit line limit if you plan to max it out.
• Set the interest rate. Enter today's rate for planning. Most HELOCs are variable; this tool holds the rate steady for illustration.
• Set draw and repayment periods. Defaults are 5 years draw and 15 years repayment—common bank structures, though yours may differ.
• Press Calculate. Compare interest-only draw payments, full P&I repayment payments, total interest, charts, and the combined amortization schedule.

Want fixed payments from day one? Compare against the Home Equity Loan Calculator. For first-mortgage payments, see the Mortgage Payment Calculator.

HELOC Formulas and Practical Applications

Picture a HELOC like a credit card secured by your house—you have a spending limit, minimum payments, and a deadline when the balance must be paid down on a fixed schedule. The two-phase structure is what makes the math tricky.

Draw period — interest only

During the draw phase you pay interest on whatever balance is outstanding. With a fully drawn amount B and annual rate r:

Draw Payment = B × (r / 100 / 12)

A $50,000 balance at 8% costs about $333 per month in interest only. No principal is paid down unless you choose to pay extra.

Repayment period — full amortization

When the draw period ends, the remaining balance amortizes over the repayment term with standard P&I payments:

Repay Payment = B × [ i(1 + i)ⁿ ] / [ (1 + i)ⁿ − 1 ]

That same $50,000 at 8% over 15 years (n = 180) jumps to about $478 per month—and every dollar now includes principal. Total interest across both phases is shown in the results table.

Variable rates and planning buffers

Most HELOCs track the prime rate plus a margin. If prime rises two percentage points, your draw payment on $50,000 adds roughly $83 per month—and the repayment payment climbs even more because the balance is amortized at the higher rate. In my experience, stress-testing at least +2% above today's quote saves a lot of surprise later. This calculator does not auto-project rate changes; re-run with a higher rate to see the buffer you need.

Frequently Asked Questions

What is the draw period on a HELOC?

The draw period—often 5 to 10 years—is when you can borrow against your line and are typically required to make interest-only payments on the outstanding balance.

What happens when the HELOC repayment period starts?

You can no longer draw funds. The outstanding balance amortizes over the repayment term with principal-and-interest payments, which are usually much higher than interest-only draw payments.

Are HELOC rates fixed or variable?

Most HELOCs have variable rates tied to a benchmark such as the prime rate. This calculator uses a fixed rate you enter for planning—it does not model future rate changes.

How is the interest-only draw payment calculated?

Monthly interest-only payment equals the drawn balance times the annual rate divided by 12.

Can I pay principal during the draw period?

Many lenders allow optional principal payments during the draw period, which reduces the balance before repayment begins. This tool assumes interest-only payments during draw unless you adjust the loan amount manually.