HELOC Calculator: Estimate Your Credit Line and Payments
A HELOC calculator estimates your available credit line and monthly payments during both the draw period and repayment period. During the draw period, you typically make interest-only payments: a $50,000 balance at 9% costs about $375/month. When the repayment period starts, payments jump to approximately $507/month (15-year amortization) as you begin paying both principal and interest.
Key Takeaways
- Draw period payments (interest-only) are significantly lower than repayment period payments
- On $50,000 at 9%: ~$375/month (draw period) vs. ~$507/month (repayment period) — a 35% increase
- Your credit line = home value × LTV cap (80–85%) − mortgage balance
- Variable rates mean your actual payments will fluctuate — calculate scenarios at current rate, +1%, and +2%
- Making principal payments during the draw period reduces repayment period payment shock
- Budget for the repayment period payment from day one, even if only interest is required during the draw period
Interest-Only Payments During the Draw Period
Most HELOCs require only interest payments during the 5–10 year draw period. This keeps your costs low but means you’re not paying down the principal. Here’s what interest-only payments look like at different balances and rates:
| Balance Drawn | At 8.0% | At 9.0% | At 10.0% | At 11.0% |
|---|---|---|---|---|
| $20,000 | $133 | $150 | $167 | $183 |
| $40,000 | $267 | $300 | $333 | $367 |
| $60,000 | $400 | $450 | $500 | $550 |
| $80,000 | $533 | $600 | $667 | $733 |
| $100,000 | $667 | $750 | $833 | $917 |
Repayment Period Payment Estimates
When the draw period ends and the repayment period begins, your payments increase significantly as you start paying both principal and interest. Here are estimates for a 15-year repayment period:
| Balance | At 8.0% | At 9.0% | At 10.0% | At 11.0% |
|---|---|---|---|---|
| $25,000 | $239 | $254 | $269 | $284 |
| $50,000 | $478 | $507 | $537 | $568 |
| $75,000 | $717 | $761 | $806 | $853 |
| $100,000 | $956 | $1,014 | $1,075 | $1,137 |
Rate Change Scenarios
Because HELOC rates are variable, it’s critical to understand how rate changes affect your payments. Here’s what happens to a $60,000 balance if rates increase from your starting rate:
| Rate Scenario | Interest-Only Payment | Amortized Payment (15-yr) | Annual Interest Cost |
|---|---|---|---|
| 9.0% (current) | $450 | $609 | $5,400 |
| 10.0% (+1%) | $500 | $645 | $6,000 |
| 11.0% (+2%) | $550 | $682 | $6,600 |
| 12.0% (+3%) | $600 | $720 | $7,200 |
Planning tip: Always stress-test your budget by calculating payments at your current rate plus 2–3 percentage points. If you can comfortably afford payments at the higher rate, you’re well-positioned to handle rate increases.
How to Calculate Your Available HELOC Credit Line
Your maximum HELOC credit line depends on your home’s value, mortgage balance, and the lender’s LTV cap. Here’s the formula:
Maximum credit line = (Home value × LTV cap) − Mortgage balance
| Home Value | Mortgage | 80% LTV Credit Line | 85% LTV Credit Line |
|---|---|---|---|
| $300,000 | $180,000 | $60,000 | $75,000 |
| $400,000 | $250,000 | $70,000 | $90,000 |
| $500,000 | $300,000 | $100,000 | $125,000 |
| $600,000 | $350,000 | $130,000 | $160,000 |
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Frequently Asked Questions
How do I calculate my HELOC interest-only payment?
Multiply your current balance by your annual interest rate, then divide by 12. For example: $50,000 × 9% ÷ 12 = $375/month. This formula gives you the exact interest-only payment during the draw period.
Why do HELOC payments increase after the draw period?
During the draw period, most lenders only require interest payments. When the repayment period starts, you must pay both principal and interest, and the balance must be fully repaid within the repayment term (10–20 years). This shift from interest-only to amortized payments typically increases payments by 25–50%.
Can I predict how my HELOC rate will change?
You can’t predict exact rate changes, but you can track Federal Reserve meeting dates and market expectations. The Fed meets 8 times per year, and financial markets price in expected rate changes. Websites like CME FedWatch show market probabilities for future rate decisions.
Should I make principal payments during the draw period?
Yes, if your budget allows it. Making principal payments during the draw period reduces your balance, which means lower interest charges and a smaller payment shock when the repayment period begins. Even small extra payments can make a significant difference over a 10-year draw period.
Last updated: March 2026. Rates and requirements are subject to change. Always verify current terms with lenders directly.