What is a HELOC and how does it work?

A Home Equity Line of Credit (HELOC) is a revolving credit line secured by your home's equity, functioning much like a credit card but with a much lower interest rate. It has two phases: a draw period (typically 10 years) where you can borrow, repay, and re-borrow — making only interest payments on the amount drawn; and a repayment period (typically 20 years) where you can no longer draw funds and must make fully amortizing payments on the balance. Most HELOCs have variable interest rates tied to the prime rate.

How is the HELOC draw period payment calculated?

During the draw period, payments are interest-only. The monthly payment equals the drawn balance times the monthly interest rate (annual rate ÷ 12). For example, $30,000 drawn at 8.5% APR produces a monthly payment of about $212.50. The principal never decreases during this phase unless you voluntarily pay it down.

What is payment shock on a HELOC?

Payment shock is the jump in your monthly payment when the draw period ends and amortization begins. Because the draw-period payment is interest-only (often just $200–$300/month) but the repayment-period payment is fully amortizing (often 2×–4× higher), many borrowers are caught off guard. The best defense is to make voluntary principal payments during the draw period to reduce the balance that will need to be amortized.

How much HELOC can I qualify for?

Lenders typically allow you to borrow up to 85% of your home's value minus your outstanding mortgage balance. On a $500,000 home with a $300,000 mortgage, your maximum HELOC would be roughly $125,000. Your credit score, income, and existing debt-to-income ratio all affect approval and rate. Most lenders require a credit score of 680+ and a combined loan-to-value (CLTV) of 85% or less.

Are HELOC interest rates fixed or variable?

Most HELOCs have variable interest rates tied to the prime rate plus a margin (e.g., prime + 0.5%). When the prime rate rises, your payment rises. Some lenders offer fixed-rate HELOCs or fixed-rate conversion options on portions of your balance, but these typically come with slightly higher initial rates. The variable nature of HELOCs is one of the key risks to plan for.

What can I use a HELOC for?

HELOCs are popular for home improvements, debt consolidation, college tuition, large medical bills, and emergency funds. The interest is tax-deductible only when the funds are used to buy, build, or substantially improve the home that secures the loan (per IRS rules, post-2017 TCJA). Using a HELOC for daily expenses or to invest is generally discouraged because your home is at risk if you can't repay.

Is a HELOC better than a home equity loan?

It depends on your needs. A home equity loan gives you a lump sum at a fixed rate — best for a one-time expense with predictable repayment. A HELOC provides a revolving line you can draw from as needed — best for ongoing or multi-stage projects. HELOCs typically have lower upfront costs but variable rates; home equity loans have higher closing costs but rate certainty. Many homeowners use a HELOC for the draw flexibility and convert portions to fixed rates as needed.

What happens at the end of the draw period?

When the draw period ends, you can no longer borrow against the line. The balance is converted to a fully amortizing loan, with monthly payments calculated to pay off the balance over the repayment period (often 20 years). Some lenders offer a balloon payment option (paying off the entire balance in one lump sum), but this is risky and should only be considered if you have a clear repayment plan. Most borrowers refinance the balance into a new loan or sell the home at this point.

HELOC Calculator

A HELOC calculator is a free online tool that estimates your home equity line of credit payments across the draw period and repayment period. It shows the two-phase balance curve, total interest, and payment-shock risk. Free, no sign-up required.

HELOC Details

Credit Limit?Enter your credit limit.

Drawn Amount?Enter your drawn amount.

Interest Rate?The annual interest rate on your mortgage loan.

Draw Period?How long you can borrow from the HELOC.

Repayment Period?How long you have to repay the HELOC.

End of inputs

Your HELOC Summary

Draw Period Payment

$212.50

10 yrs interest-only

Repayment Payment

$260.35

20 yrs amortizing

Drawn Amount

$30,000.00

60.00% of limit

Draw Period Interest

$25,500.00

Interest-only total

Repayment Interest

$32,482.12

Amortizing total

Total Interest

$57,982.12

Over 360 months

Credit limit: $50,000.00. Drawn: $30,000.00 (60.00% utilized). Rate: 8.50%. Draw period: 10 years interest-only at $212.50/mo. Repayment: 20 years amortizing at $260.35/mo. Payment shock: 1.23× (manageable).

Two-Phase Balance Curve

Key Insights

Over the 10-year draw period you'll pay $25,500.00 in interest without reducing the principal. That's 85.00% of the drawn balance — and the full $30,000.00 is still owed at the end. Pay principal voluntarily during the draw period to avoid a much larger repayment bill later.

You're using 60.00% of your credit line. That's a moderate drawdown — manageable, but consider whether further draws are necessary. Each additional draw increases your interest-only payment and reduces flexibility.

Your 20-year repayment term is on the long end — you'll pay $32,482.12 in interest alone, more than the balance. A 10–15 year term costs more monthly but dramatically less total interest.

Your rate of 8.50% is in the typical HELOC range. Because the rate is variable, your payment could rise (or fall) with the prime rate. Monitor rate environment; consider voluntary principal payments to reduce exposure.

Your payment will increase by about 22.52% when amortization begins — from $212.50/mo to $260.35/mo. A modest, manageable jump.

Guide

How to Use This Calculator

1Enter your total credit limit (the maximum amount you can borrow against your home equity).
2Set the drawn amount — the balance you currently owe. This cannot exceed the credit limit.
3Adjust the interest rate to match your lender's current rate. Most HELOCs are variable.
4Set the draw period length in years (typically 5–10 years). During this phase, payments are interest-only.
5Set the repayment period length in years (typically 10–20 years). After the draw period, payments become fully amortizing.
6Review the two monthly payments: interest-only during the draw period and the higher amortizing payment during repayment.
7Examine the two-phase balance curve chart — flat during the draw, then declining during the repayment period.
8Read the AI-powered insights for risk flags around utilization, payment shock, and variable-rate exposure.

Formula

How It's Calculated

HELOC payments split into two phases:

DRAW PERIOD (interest-only):
  monthlyPayment = drawnBalance × (rate ÷ 12)
  totalDrawInterest = monthlyPayment × (drawYears × 12)

REPAYMENT PERIOD (amortizing):
  monthlyPayment = P × [r(1+r)^n] / [(1+r)^n − 1]
  where:
    P = drawnBalance
    r = rate ÷ 12
    n = repaymentYears × 12
  totalRepaymentInterest = (monthlyPayment × n) − drawnBalance

TOTAL INTEREST = totalDrawInterest + totalRepaymentInterest

Example: $30,000 drawn at 8.5% APR, 10-year draw, 20-year repayment
  Draw payment       = 30,000 × (0.085/12) = $212.50/mo
  Draw total interest = $212.50 × 120       = $25,500
  Repayment payment   = ~$260.62/mo (amortizing $30k at 8.5%/240mo)
  Repayment interest  = $260.62 × 240 − $30,000 = ~$32,548
  Total interest      = $25,500 + $32,548  = ~$58,048
  Payment shock       = $260.62 / $212.50  = 1.23× (manageable)

Note: HELOC interest is tax-deductible only when used to buy, build, or
substantially improve the home securing the loan. Consult a tax professional
for your specific situation.

Glossary

Key Terms

FAQ

Frequently Asked Questions

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