HELOC Payment Calculator

• Models both the draw period (interest-only or 1% minimum) and the repayment period as a standard amortizing loan.
• Shows the payment jump between phases, which surprises many HELOC borrowers.
• Lets you test how a small extra payment during the draw period changes total interest.
• Uses a single flat rate for the estimate — real HELOC rates are variable and will differ over time.

How to use this calculator

Enter the balance currently drawn on the line — not your total credit limit, but what you've actually borrowed — along with the interest rate, the draw period payment type, and the length of each phase. The calculator produces today's payment and the payment once the repayment period begins, along with the combined schedule across both.

Under Advanced, you can add a voluntary extra monthly payment during the draw period. This is optional on a real HELOC — the required payment during the draw period is usually just interest, or a small minimum — but paying more now reduces both the balance carried into repayment and the total interest paid over the life of the line.

The two phases of a HELOC

A home equity line of credit is revolving credit secured by your home, similar in structure to a credit card but usually at a much lower rate. It has two phases:

• The draw period (commonly 5–15 years). You can borrow, repay and re-borrow against the line up to your credit limit. Many HELOCs only require an interest-only or small minimum payment during this phase.
• The repayment period (commonly 10–20 years). The line stops revolving — you can no longer draw against it — and whatever balance remains amortizes like a standard loan, with a payment that includes both principal and interest.

The jump between these two payments can be significant, especially if the draw-period payment was interest-only and the balance never fell.

How the payments are calculated

During the draw period, this calculator applies your chosen payment type each month: interest-only means the payment simply covers that month's interest charge, leaving the balance unchanged; the 1%-minimum option pays the larger of the interest or 1% of the balance, so a small amount of principal is retired each month even without an extra payment.

Interest-only payment = balance × (annual rate ÷ 12)
1% minimum payment    = max( interest, balance × 1% )

Whatever balance remains when the draw period ends becomes the starting principal for a standard fixed-rate amortizing loan over the repayment period you selected, using the same formula as the Amortization Schedule calculator.

A worked example

A $50,000 balance at 8.5%, interest-only during a 10-year draw period, produces a payment of about $354 a month — and because none of that reduces the balance, the full $50,000 still needs to be repaid when the 10 years end. Spread over a 15-year repayment period at the same rate, that produces a new payment of roughly $492 a month, a jump of about 39% from the draw-period payment.

Adding just $150 a month toward principal during the draw period would bring the balance carried into repayment down meaningfully, lowering both the size of that payment jump and the total interest paid across both phases.

Assumptions and limitations

• The rate is held flat. Real HELOCs are almost always variable, tied to the prime rate plus a margin. Your actual payment will move as that index moves — this calculator cannot predict future rate changes.
• No further draws are modelled. This assumes you draw the balance entered and then either pay it down or leave it — not that you continue drawing against the line during the draw period.
• Repayment is assumed to fully amortize. Some HELOCs offer a balloon payment or other structure at the end of the draw period instead of a standard amortizing repayment period — check your specific loan terms.
• No annual fees, draw fees or early-closure fees are included.

Common mistakes

Assuming the draw-period payment is what you'll always pay. The most common and most expensive misunderstanding — if the draw-period payment is interest-only, the balance genuinely does not fall on its own, and the repayment-period payment can be a real shock without planning.

Ignoring rate variability. Because HELOC rates are usually variable, a payment that is affordable today can become materially less affordable if rates rise before or during repayment.

Treating the credit limit as the balance owed. Interest and payments are based on what you've actually drawn, not your total available credit line.

Frequently asked questions