This HELOC payment calculator shows your interest-only draw payment, your amortized repayment phase payment, the payment jump, and total interest paid.
HELOC Payment Formula
A HELOC has two phases with two different payments. During the draw period, most lenders require interest-only payments on the drawn balance:
Pdraw = B * r / 1200
When the draw period ends, the balance is amortized over the repayment period using the standard loan payment formula:
Prepay = B * i / (1 - (1 + i)^-n) i = r / 1200 n = Y * 12
Variables:
- B is the HELOC balance (the amount actually drawn, not the credit limit)
- r is the annual interest rate as a percent
- Pdraw is the interest-only monthly payment during the draw period
- Prepay is the fully amortized monthly payment during the repayment phase
- i is the monthly interest rate as a decimal
- Y is the length of the repayment period in years and n is that length in months
Enter your drawn balance and interest rate, then choose how many years remain in your draw period and how long your repayment period runs (10-year draw with 20-year repayment is the most common structure). The calculator returns your current interest-only payment, the larger payment that starts when the draw period ends, the size of that payment jump, and the total interest you would pay if you only ever made minimum payments.
Because interest-only payments never touch principal, the balance at the end of the draw period is the same as today’s balance, and every dollar of those draw-phase payments is pure interest. The results assume the rate holds steady, but HELOC rates are variable, so treat the numbers as a snapshot at today’s rate.
Interest-Only vs Repayment Payments at 8.5%
This table compares the two payment phases at an 8.5% rate with a 10-year draw period and a 20-year repayment period, the most common HELOC structure. Total interest assumes minimum payments in both phases.
| Balance drawn | Interest-only payment | Repayment payment | Payment jump | Total interest |
|---|---|---|---|---|
| $25,000 | $177.08 | $216.96 | +$39.87 | $48,319.39 |
| $50,000 | $354.17 | $433.91 | +$79.74 | $96,638.79 |
| $75,000 | $531.25 | $650.87 | +$119.62 | $144,958.18 |
| $100,000 | $708.33 | $867.82 | +$159.49 | $193,277.58 |
| $125,000 | $885.42 | $1,084.78 | +$199.36 | $241,596.97 |
| $150,000 | $1,062.50 | $1,301.73 | +$239.23 | $289,916.36 |
Example Problems
Example 1: Find both payments on a $50,000 draw.
You have drawn $50,000 on a HELOC at 8.5% with 10 years left in the draw period and a 20-year repayment period. The interest-only payment is:
Pdraw = 50,000 * 8.5 / 1200 = $354.17 per month. Amortizing $50,000 over 240 months at 8.5% gives Prepay = $433.91, a jump of $79.74 per month. Minimum payments cost $42,500.00 in interest during the draw period and $54,138.79 during repayment, for total interest of $96,638.79.
Example 2: A larger draw at a higher rate with a shorter schedule.
You have drawn $100,000 at 9% with 5 years left in the draw period and a 15-year repayment period. Pdraw = 100,000 * 9 / 1200 = $750.00 per month, and the repayment-phase payment is $1,014.27, a jump of $264.27. Interest comes to $45,000.00 during the draw phase plus $82,567.99 during repayment, for total interest of $127,567.99.
Frequently Asked Questions
Why does my HELOC payment jump after the draw period?
During the draw period you typically pay interest only, so nothing goes toward the balance. When the draw period ends, the loan converts to fully amortizing payments that must retire the entire balance over the repayment period, so principal is added on top of interest. The jump is largest when the repayment period is short relative to the balance, and it can be substantial if you carried a large draw the whole time.
What determines a HELOC’s interest rate?
Almost all HELOCs are variable-rate loans priced at the prime rate plus a margin, and the margin is set by your credit score, your combined loan-to-value ratio, and the lender’s pricing. When the Federal Reserve moves rates, prime moves with it and your HELOC rate follows, usually the next billing cycle. Some lenders offer fixed-rate lock options on portions of the balance for a fee or a slightly higher rate.
Can I pay down principal during the draw period?
Yes, and it is usually smart. Interest-only is the minimum, not a rule, so any extra you pay reduces the balance, cuts every future interest charge, and shrinks the payment jump at the end of the draw period. Because a HELOC is revolving credit, principal you repay during the draw period is also available to borrow again if you need it.
