Direct Answer
A HELOC (home equity line of credit) amortization schedule covers two phases: an optional interest-only draw period, then repayment that amortizes the drawn balance. Example: $40,000 drawn at 8% costs about $267/month interest-only; amortizing over 20 years rises to about $335/month. Model both phases with the HELOC Calculator. For closed-end interest-only then amortize loans, use the Amortization Calculator.
Last verified on: July 13, 2026
Editorial note: HELOC rates are often variable. Examples use fixed planning rates. Not a Loan Estimate or lending advice.
Research method: Interest-only dues = balance * monthly rate; repayment phase uses standard amortization. Verified July 13, 2026.
Draw period vs repayment period
| Phase | Typical payment | Balance behavior |
|---|---|---|
| Draw period | Interest-only on amount drawn (common) | Flat if you pay IO only; falls if you pay extra principal |
| Repayment period | Fully amortizing payment on remaining draw | Declines to zero over the repayment term |
Many HELOCs last 10 years draw + 20 years repayment (30 years total), but products vary.
Formulas you need
Interest-only monthly payment:
IO payment = P * (annual rate ÷ 12)Amortizing monthly payment (repayment phase):
M = P * [r(1 + r)^n] / [(1 + r)^n - 1]- P = amount still drawn when amortization starts
- r = monthly rate
- n = repayment months
Three worked examples
Example 1 — Classic HELOC: $40,000 drawn at 8%
| Phase | Payment | What happens to principal |
|---|---|---|
| Interest-only | $266.67/mo | Balance stays $40,000 if you pay IO only |
| Repayment, 20 years | $334.58/mo | Balance amortizes to $0; total interest in repayment ≈ $40,300 |
Year-1 IO cost: 12 * $266.67 ≈ $3,200 — and you still owe $40,000.
Takeaway: IO keeps cash flow low during renovations, but every IO year is pure cost. Paying even $100 extra principal during draw both cuts IO dues and shrinks the later $335 payment.
Example 2 — Larger draw, shorter repay: $75,000 at 7.5%, 15-year amortize
| Phase | Payment |
|---|---|
| Interest-only on $75,000 | $468.75/mo |
| Amortize over 15 years | $695.26/mo |
Payment jump: about +$226/month when repayment starts — before any rate reset.
If you instead amortize the same $75,000 over 20 years at 7.5%:
M ≈ $604/moVariation insight: Stretching repayment lowers the post-draw payment (~$604 vs ~$695) but raises lifetime interest. Choose based on budget stress at the IO→amortize cliff, not only today’s IO bill.
Example 3 — Interest-only mortgage style: $300,000 at 6% for 5 years IO, then 25 years amortize
This mirrors many interest-only mortgage schedules (closed-end), useful if you searched for an interest-only amortization schedule rather than a HELOC.
| Phase | Years | Monthly P&I |
|---|---|---|
| Interest-only | 5 | $1,500 |
| Amortize remaining $300,000 | 25 | $1,933 |
| Compare: fully amortizing 30-year from day one | 30 | $1,799 |
Interest in 5 IO years: 5 * 12 * $1,500 = $90,000, with $300,000 still owed.
Variation insight: Full 30-year amortization costs ~$1,799/month from day one — higher than IO, lower than the post-IO $1,933 payment, and it builds equity immediately. IO only wins if you have a planned principal event (sale, refinance, large lump sum) before amortization starts.
How to read a HELOC schedule in the calculator
- Enter credit limit, amount drawn, rate, draw years, and repayment years in the HELOC Calculator.
- Keep interest-only during draw checked to match most statements.
- Review the repayment amortization table for the drawn balance.
- Stress-test a +1% rate scenario because HELOC APRs often adjust.
For a fixed installment comparison (home equity loan), see HELOC vs home equity loan.
Related Reading
- HELOC vs home equity loan — fixed lump sum vs revolving line
- HELOC vs cash-out refinance — which equity path fits
- Personal & business loan amortization — standard installment schedules
- Amortization formula explained
- Mortgage recast vs refinance — lump-sum payment relief options
Official and supporting sources
- CFPB — What is a home equity line of credit (HELOC)?
- CFPB — HELOC vs home equity loan
- CFPB — HELOC brochure (PDF)
- Federal Reserve — Consumer credit (G.19)
Frequently Asked Questions
What is a HELOC amortization schedule?
A HELOC amortization schedule shows how payments pay down the drawn balance after the interest-only draw period ends (or during draw if your HELOC requires principal reduction). In repayment, the payment is set so the outstanding draw amortizes over the repayment term — similar to a fixed installment loan, though many HELOCs still use a variable rate. The HELOC Calculator estimates draw-period interest-only dues and a repayment amortization table for the amount drawn.
How does interest-only amortization work?
During an interest-only period, the payment equals balance * monthly rate, so the principal does not fall. On $40,000 at 8%, interest-only is about $267/month. When amortization begins, the payment jumps because you must also retire principal. Interest-only mortgage or HELOC schedules therefore show flat balances for years, then a steeper amortizing curve.
Why did my HELOC payment jump after the draw period?
You likely moved from interest-only (or low principal) payments into full amortization of whatever you still owe. If you drew $75,000 and rates are 7.5%, interest-only is about $469/month; amortizing that balance over 15 years is about $695/month — before any rate change. Paying down principal during the draw period softens the jump.
Can I amortize a HELOC early?
Yes. Extra principal during the draw period reduces both interest-only dues and the later amortizing payment. Some borrowers convert a HELOC balance to a fixed home equity loan for payment certainty — compare options in our HELOC vs home equity loan guide. Always confirm variable-rate resets and prepayment rules with your lender.
Is an interest-only mortgage schedule the same as a HELOC?
The interest-only math is the same: payment = principal × monthly rate. Product rules differ. HELOCs are revolving during the draw period; interest-only mortgages are usually closed-end with a planned IO term then amortization or balloon. Use the Amortization Calculator for closed-end IO-then-amortize scenarios and the HELOC Calculator for line-of-credit draw plus repayment.
How do I build a HELOC repayment schedule myself?
Take the balance you expect at the end of the draw period as P, use your estimated repayment annual percentage rate (APR) as the annual rate, and set n to repayment months. Apply M = P * r(1+r)^n / ((1+r)^n - 1), then build month rows like any amortizing loan. The HELOC Calculator automates this and shows interest-only dues for the draw phase.
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