HELOC Calculator
What a home equity line costs while you are drawing on it — and what the payment becomes on the day that stops, which is the part people are surprised by.
The address carries whatever you changed, so anyone opening it sees these numbers. Nothing is saved on our side.
Payment during the draw period
$567/mo
Interest only, so none of it reduces the balance. When the draw period ends the payment becomes $788 — 1.39× higher.
- $567
- Interest only
- $788
- 1.39× higher
- $68,000
- Buys no principal
- $129,803
- $130,000
- $788
- $61,803 interest
What is actually borrowable
Equity owned and equity lendable are different numbers. A lender caps what may be owed against the home in total, not what you have built up.
- First mortgage63%$380,000
- Available to borrow22%$130,000
- Equity the lender leaves untouched15%$90,000
- Home value$600,000
The payment when the draw period ends
Nothing about the balance changes on that date. The time left to repay it does.
You pay $567 a month for 10 years — $68,000 in total — and still owe $80,000.
Then the payment becomes $788, 1.39 times what you had been paying, because that balance now has to clear in 15 years. A shorter repayment period makes it steeper still.
How this calculator works
Two payments, because a HELOC is really two loans in sequence.
During the draw period
payment = balance × rate ÷ 12
After it ends
M = L · r ÷ (1 − (1 + r)−n)
L in the second formula is the full amount drawn, because the first formula never touched it. That is the entire reason the payment jumps.
What is assumed
- A fixed rate. Most HELOCs are variable, and a projection cannot know where rates go.
- You draw the full amount at the start and repay none of it during the draw period — the worst case, and a common one.
- No annual fee, draw fee or early-closure charge.
A worked example
$80,000 drawn at 8.5%, a ten-year draw period and fifteen years to repay.
| Payment during the draw | 80,000 × 8.5% ÷ 12 |
|---|---|
| Paid over ten years | 566.67 × 120 |
| Balance still owed | Unchanged, because nothing repaid it |
| Payment after the draw | 80,000 at 8.5% over 180 months |
| The jump | 787.79 ÷ 566.67 |
$68,000 paid, and the debt is exactly where it started. That is what interest-only means, and it is worth seeing as a number rather than a definition.
The 1.39× jump here is mild because there are fifteen years to repay. Set the repayment period to five and the payment becomes $1,641 — 2.9 times what the borrower had been paying, on a balance they had been servicing comfortably for a decade. Check your repayment period before you check the rate.
Questions people ask
Nothing about the balance changes on that date — only the time left to repay it. During the draw period the payment was interest only, so the balance is exactly what you drew. It now has to amortize over the repayment period, and the payment rises accordingly. On $80,000 at 8.5%, it goes from $566.67 to $787.79 with fifteen years to repay, and to over $1,600 with five.
Because it is not repaying anything. An interest-only payment covers the cost of the money and no more. Ten years of it on $80,000 at 8.5% costs $68,000 and leaves you owing $80,000 — the same balance you started with.
Monthly, at first, almost always. In total, no. Paying nothing off for a decade cannot be cheaper than amortizing from day one, and the calculator will show you the gap on your own numbers. The HELOC's advantages are flexibility — you draw what you need when you need it — and a lower initial payment, not lower cost.
Usually not. Most are variable, tied to a published index plus a margin, so both payments move with rates. This calculator models a fixed rate because a projection cannot know where rates will go. Treat the figures as what happens if the rate stays where it is, and ask your lender about the lifetime cap.
Almost always, and it is the single best thing you can do with one. Every dollar repaid during the draw period reduces both the interest you pay and the payment shock when it ends. The trap is not the product — it is treating the minimum payment as the plan.
Related calculators
An estimate at a fixed rate. Most HELOCs are variable, so both payments move with rates. It excludes annual fees, draw fees and early-closure charges.