HELOC Payment Calculator
A fast, private home equity line of credit calculator to estimate your maximum borrowing limit, draw period payments, and repayment phase costs.
- Payment Type: Interest-Only
- Initial Drawn Amount: $50,000.00
- Monthly Principal Paid: $0.00/mo
- Cumulative Draw Interest: $42,500.00
- Balance at Repayment Start: $50,000.00
- Payment Type: Principal + Interest
- Repayment Duration: 20 Years (240 mo)
- Line Status: Closed to New Draws
- Cumulative Repay Interest: $54,138.79
- Ending Loan Balance: $0.00 (Paid Off)
Full 30-Year HELOC Lifetime Cost Summary
- Total Principal Borrowed $50,000.00
- Total Lifetime Interest $96,638.79
- Total Cash Paid Over Life $146,638.79
| Year | Phase | Annual Payment | Principal Paid | Interest Paid | Ending Balance |
|---|
How to Use This Calculator
- Enter Your Home Value and Mortgage Balance: Enter your property's estimated current market value and what you currently owe on your primary mortgage.
- Select Your Lender's Maximum CLTV: Choose your lender's allowable Combined Loan-to-Value limit (typically 80% or 85%). The calculator immediately computes your maximum available borrowing line.
- Input Your Planned Draw and Rate: Specify how much cash you actually intend to withdraw and the estimated variable APR.
- Analyze Your Payment Shock: Review the large payment forecast card to see exactly how much your monthly payment will increase when the interest-only draw period ends and mandatory principal repayment begins.
The Formula
A Home Equity Line of Credit consists of two separate mathematical phases: borrowing capacity evaluation and dual-phase amortization.
1. Maximum Borrowing Line (Combined LTV)
For instance, an $450,000 home with an 80% allowable CLTV yields a maximum cumulative borrowing ceiling of $360,000. Subtracting a $250,000 primary mortgage leaves a maximum HELOC credit line of $110,000.
2. Phase 1: Draw Period Interest-Only Payment
Because no principal repayment is required during the draw phase, your entire monthly bill covers only the interest accrued on the funds you have borrowed.
3. Phase 2: Repayment Period Amortization
Where r is the monthly interest rate (APR ÷ 12) and n is the remaining repayment term in months (e.g., 20 years = 240 monthly installments).
4. Payment Shock Calculation
% Jump = [ Payment Shock ÷ Monthly Draw Payment ] × 100
Example: Navigating the 10-Year Draw Transition
Imagine a homeowner with a $450,000 home and a $250,000 primary mortgage who opens a HELOC with an 80% CLTV limit at an 8.50% APR:
- Maximum Credit Limit: ($450,000 × 0.80) - $250,000 = $110,000.
- Actual Amount Drawn: The homeowner draws $50,000 for a major kitchen remodel.
Phase 1: Draw Period (Years 1 to 10)
- Monthly Payment: $50,000 × (0.085 ÷ 12) = $354.17 per month (interest-only).
- Cumulative Draw Interest: $354.17 × 120 months = $42,500.00.
- Balance at Year 10: Still $50,000.00 (because zero principal was paid).
Phase 2: Repayment Period (Years 11 to 30)
- New Monthly Payment: Fully amortized over 20 years (240 months) at 8.50% APR = $433.91 per month.
- The Payment Shock: The monthly payment jumps from $354.17 to $433.91—an increase of +$79.74 per month (+22.5%).
- Cumulative Repayment Interest: $54,138.79.
- Total Lifetime Interest Paid: $42,500.00 + $54,138.79 = $96,638.79 ($146,638.79 total cash outlay).
Frequently Asked Questions
How is a HELOC monthly payment calculated?
During the draw period (typically 10 years), most lenders require interest-only payments calculated as your drawn balance multiplied by your monthly interest rate (annual APR divided by 12). During the repayment period (typically 20 years), the line closes to new borrowing and converts into a fully amortized loan requiring monthly payments of both principal and interest.
How much can I borrow with a home equity line of credit?
Your maximum borrowing capacity is determined by your lender's Maximum Combined Loan-to-Value (CLTV) limit, usually between 80% and 85%. Multiply your home's current market value by the CLTV percentage and subtract your existing primary mortgage balance to determine your available line of credit.
What is the difference between the draw period and the repayment period?
The draw period is the initial borrowing phase where you can withdraw and reuse cash as needed, typically with low, interest-only payments. The repayment period starts once the draw period concludes; you can no longer withdraw funds, and your monthly payments increase to pay off the remaining principal balance.
What is HELOC payment shock and how can I prepare for it?
Payment shock is the dramatic surge in your monthly bill when transitioning from the interest-only draw phase to the fully amortizing repayment phase, often increasing payments by 30% to 100%. You can prevent payment shock by voluntarily paying down principal during the draw phase, refinancing into a fixed-rate loan, or budgeting for the higher payment in advance.
What is the difference between a HELOC and a traditional home equity loan?
A HELOC is a revolving line of credit with variable interest rates that allows you to borrow and repay funds flexibly as needed. A traditional home equity loan provides a single lump-sum payout upfront with a fixed interest rate and fixed monthly principal-and-interest payments starting immediately.