HELOC Calculator
See how big a home equity line of credit you qualify for, your interest-only draw payment, and the payment shock when repayment begins. Defaults to the live Prime Rate.
HELOCs feel cheap during the draw — about $550/mo interest-only on a $100,000 balance — then jump to $751/mo (1.37×) at repayment (Q2 2026).
6.6%
current US Prime Rate (Fed Funds + 3) — HELOCs price near this — FRED (Q2 2026)
$125,000
example line on a $500k home with a $300k mortgage at an 85% CLTV cap
1.37×
payment jump from interest-only draw to full repayment on a $100,000 balance (Q2 2026)
Borrow against your home — with eyes open
A HELOC is flexible and often cheap, but the variable rate and payment shock catch many borrowers out.
Your line comes from your equity
Lenders lend against the equity you've built, capped by a combined loan-to-value limit (usually 80–85%). The bigger your equity and the smaller your mortgage, the larger the line. On a $500k home owing $300k at 85% CLTV, that's up to about $125,000.
Mind the payment shock
Interest-only payments during the draw feel affordable — about $550/mo in this example — but when repayment starts the payment can jump to $751/mo (1.37×). The payment-over-time chart shows exactly when and how much.
Variable rate, moving target
HELOC rates follow Prime (about 6.6% now, Q2 2026) plus a lender margin, so they rise and fall with Fed policy. A HELOC can be cheaper than other unsecured credit, but budget for rate increases — your payment is not fixed.
How the HELOC Calculator Works
Formula
Current Equity = Home Value − Mortgage Balance
Max Line = (Home Value × Max CLTV%) − Mortgage Balance
Draw period (interest-only):
Monthly Payment = Balance × (APR ÷ 12)
Repayment period (amortizing):
Monthly Payment = Balance × r ÷ (1 − (1 + r)^−n) (r = APR/12, n = repay years × 12)
Default APR ≈ Prime = effective Fed Funds + 3Enter your home value
An estimate of what your home is worth today.
Enter your mortgage balance
What you still owe (0 if paid off).
Set the CLTV cap
The lender's combined loan-to-value limit — usually 80–85%.
Choose how much to draw
The calculator clamps it to the line you qualify for.
Set rate and periods
Rate defaults to Prime (6.6%, Q2 2026); set draw and repayment lengths.
A HELOC turns home equity into a flexible, revolving credit line. The amount you can borrow is governed by the combined loan-to-value cap: the more equity you hold relative to your mortgage, the larger the line. Because it's secured by your home, the rate is usually lower than credit cards or personal loans.
The catch is structure and rate. Interest-only payments during the draw period are low and can lull borrowers into over-borrowing; when repayment begins, the payment can more than double. And because the rate tracks Prime, it moves with Fed policy. Modelling the payment shock up front is the single most important step.
Frequently Asked Questions
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