What Is a HELOC?
A Home Equity Line of Credit (HELOC) lets you borrow against your home's equity as a revolving credit line, similar to a credit card. Unlike a home equity loan that gives you a lump sum, a HELOC lets you draw funds as needed during the draw period and then repay the balance during a separate repayment period.
HELOCs are popular for home renovations, ongoing expenses, and financial emergencies because of their flexibility. Rates are typically variable, meaning your payment can change over time as market rates shift.
Inputs Required
- Home Value: Current estimated market value of your property
- Mortgage Balance: Remaining balance on your primary mortgage
- Draw Amount: Amount you plan to draw from the HELOC
- Interest Rate: Current variable rate offered by the lender
- Draw Period: How long you can borrow from the line (typically 5 to 15 years)
- Repayment Period: How long you have to repay the balance after the draw period ends
Outputs Provided
- Draw Period Payment: Interest-only monthly payment during the draw period
- Repayment Period Payment: Fully amortizing payment once the draw period ends
- Total Interest: Combined interest across both periods
- CLTV: Combined loan-to-value ratio to check lender eligibility
How the Calculation Works
Draw Period Payment = Draw Amount x (Rate / 12)
Repayment Payment = Standard amortization on draw balance
CLTV = (Mortgage Balance + Draw Amount) / Home Value x 100
During the draw period, you pay interest only on the amount drawn. When the draw period ends, the outstanding balance becomes fully amortizing, meaning you pay both principal and interest. This transition causes a significant jump in monthly payments, sometimes called payment shock.
Most lenders require a combined loan-to-value ratio at or below 85%, meaning the total of your mortgage and HELOC cannot exceed 85% of your home's value. The exact limit depends on the lender, your credit score, and your income.
How to Use the Calculator
- Enter your home's current market value
- Input your remaining mortgage balance
- Enter the amount you plan to draw from the HELOC
- Input the current interest rate from your lender
- Select your draw period and repayment period lengths
- Toggle between draw and repayment views to compare payments
- Check the CLTV indicator to confirm eligibility
Example Calculation
A homeowner with a $400,000 home and $250,000 mortgage opens a HELOC and draws $40,000 at 9% with a 10-year draw period and 20-year repayment period:
- Available equity: $150,000
- CLTV: ($250,000 + $40,000) / $400,000 = 72.5% (within 85% limit)
- Draw period monthly payment (interest-only): approximately $300
- Repayment period monthly payment: approximately $360
- Total interest over full term: approximately $50,400
Real World Scenarios
Staged Home Renovation
A homeowner plans a $60,000 renovation in phases over three years. A HELOC lets them draw money as each phase begins rather than borrowing a lump sum upfront. They only pay interest on what they have actually used, which reduces costs compared to taking the full amount at once.
Emergency Financial Buffer
A self-employed professional opens a HELOC as a financial safety net. The credit line is available if income dips, but they only pay interest if they draw from it. Having the line open costs nothing unless used, making it a low-cost emergency reserve.
Education Funding
A parent funds a child's four-year university education by drawing $15,000 per year from a HELOC rather than taking a single $60,000 loan. The interest-only draw period keeps payments manageable while school is in session, and full repayment begins after graduation.
Why This Calculation Matters
The biggest risk with a HELOC is payment shock. When the draw period ends, your payment can increase significantly because you now pay principal plus interest on the full balance. Understanding both phases before you open the line helps you plan for the transition and avoid financial strain.
Because HELOC rates are variable, your actual payments may differ from this estimate if rates change. Use this calculator as a baseline and factor in potential rate increases when planning your budget.
Common Mistakes to Avoid
- Treating the draw period as free money: Interest-only payments mean your principal balance does not shrink during the draw period. You still owe the full amount drawn at the end
- Not planning for rate increases: HELOC rates are tied to the prime rate. A 2% rate increase on a $50,000 balance adds about $83 per month to your payment
- Drawing the maximum available: Borrowing the maximum reduces your financial flexibility and raises your CLTV, which can affect refinancing options later
- Confusing HELOC with home equity loan: A HELOC is a revolving credit line with a variable rate. A home equity loan is a fixed lump sum with a fixed rate. Choose based on whether your need is ongoing or one-time