HELOC Calculator
Estimate your home equity line of credit. See max available credit, interest-only draw payments and amortized repayment payments from your home value and rate.
Updated 2026-06-14 · Free · No sign-up · Runs privately in your browser
Show the formula & steps
How the HELOC Calculator Works
A home equity line of credit (HELOC) lets you borrow against the equity in your home. This calculator shows your maximum available credit, your interest-only payment during the draw period, and your amortized payment during the repayment period. Enter your home value, mortgage balance, maximum combined loan-to-value (CLTV), the amount you plan to borrow, the interest rate, and the repayment term.
The Formula
Max available credit = home value × max CLTV% − mortgage balance Monthly rate r = APR ÷ 12 Interest-only payment = balance × r Repayment payment = P × r ÷ (1 − (1 + r)^−n) where n = repayment years × 12
The interest-only payment applies during the draw period, when many HELOCs require only interest. The amortizing formula applies once the repayment period begins and you must pay down principal as well.
Worked Example
For a $450,000 home with a $250,000 mortgage, an 85% max CLTV, a $80,000 draw, an 8.5% APR, and a 20-year repayment term:
- Max available = 450,000 × 0.85 − 250,000 = 382,500 − 250,000 = $132,500
- Monthly rate r = 8.5% ÷ 12 ≈ 0.7083%
- Interest-only payment = 80,000 × 0.007083 ≈ $566.67/month
- Repayment payment = 80,000 × 0.007083 ÷ (1 − 1.007083^−240) ≈ $694.26/month
Because $80,000 is below the $132,500 available, the full draw is used.
Why a HELOC Calculator Helps
Knowing both payment types prevents payment shock when the draw period ends:
- Plan for the jump — interest-only payments can roughly double once principal repayment begins.
- Right-size your draw — borrow only what you need to keep payments manageable.
- Stress-test rates — variable HELOC rates can rise, so model a higher APR before committing.
| Draw amount | APR | Interest-only/mo | Repayment/mo (20 yr) |
|---|---|---|---|
| $50,000 | 8.5% | ≈ $354.17 | ≈ $433.91 |
| $80,000 | 8.5% | ≈ $566.67 | ≈ $694.26 |
| $100,000 | 8.5% | ≈ $708.33 | ≈ $867.82 |
Frequently asked questions
How much can I borrow with a HELOC?+
Lenders cap your combined loan-to-value, often around 80-90%. Multiply your home value by the max combined LTV, then subtract your current mortgage balance. For a $450,000 home at 85% CLTV with a $250,000 mortgage, you could access up to $382,500 − $250,000 = $132,500.
How are HELOC payments calculated?+
During the draw period most HELOCs are interest-only, so the monthly payment is the outstanding balance times the monthly rate (APR divided by 12). In the repayment period the balance amortizes, so the payment uses the standard loan formula P × r ÷ (1 − (1 + r) raised to the power −n).
What is the difference between the draw and repayment periods?+
The draw period (often 10 years) lets you borrow and repay flexibly, usually paying only interest. After it ends, the repayment period (often 10-20 years) begins, no more borrowing is allowed, and you pay principal plus interest until the balance reaches zero.
Are HELOC rates fixed or variable?+
Most HELOCs carry a variable rate tied to the prime rate, so your payment can rise or fall over time. This calculator uses a single rate you enter; rerun it with a higher rate to stress-test how a rate increase would affect your interest-only and repayment payments.
Does borrowing less reduce my HELOC payment?+
Yes. Both the interest-only and the amortized repayment payments scale directly with the balance you draw. Borrowing only what you need, rather than your full available credit, keeps interest charges and monthly payments lower throughout the life of the line.