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HELOC Calculator

Estimate your available home equity line of credit and project monthly payments during the draw and repayment periods. Enter your home value, mortgage balance, and HELOC terms to see how much you can borrow and what it will cost.

A Home Equity Line of Credit (HELOC) is a revolving credit line — like a giant credit card — secured by the equity in your home. You apply once, the lender approves a credit limit, and then you can draw against it as needed during the "draw period" (typically 10 years). After the draw period ends, the line closes and you enter the "repayment period" (typically 10–20 years), during which you pay back both principal and interest on whatever balance remains.

The mechanics are different from a fixed home equity loan (which is a lump-sum loan amortized from day one). A HELOC is more like a credit card: you only owe interest on what you've actually drawn, the rate is typically variable (often Prime + a margin), and you can draw, repay, and re-draw repeatedly during the draw period. During the draw years, payments are often interest-only — which makes the monthly cost very low but means you're not chipping away at the principal.

This calculator estimates your available credit (based on home value, mortgage balance, and lender LTV cap), shows what an example draw would cost monthly during the draw period (interest-only) and during the repayment period (fully amortizing), and highlights the "payment shock" when the two phases transition. Use it to test whether a HELOC is the right tool, and to plan around the eventual repayment ramp.

Inputs

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Most lenders cap at 80-85% combined LTV

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Results

Max Available Credit

$132,500

Interest-Only Payment

$354

During draw period

Full Payment

$434

During repayment

Total Interest

$96,639

Monthly Payment by Phase

Balance Over Time

Year-by-Year Breakdown

YearPhasePaymentInterestPrincipalBalance
1Draw$354.17$4,250.00$0.00$50,000.00
2Draw$354.17$4,250.00$0.00$50,000.00
3Draw$354.17$4,250.00$0.00$50,000.00
4Draw$354.17$4,250.00$0.00$50,000.00
5Draw$354.17$4,250.00$0.00$50,000.00
6Draw$354.17$4,250.00$0.00$50,000.00
7Draw$354.17$4,250.00$0.00$50,000.00
8Draw$354.17$4,250.00$0.00$50,000.00
9Draw$354.17$4,250.00$0.00$50,000.00
10Draw$354.17$4,250.00$0.00$50,000.00
11Repayment$433.91$4,211.82$995.11$49,004.89
12Repayment$433.91$4,123.87$1,083.07$47,921.81
Last updated: Reviewed by the CalcMountain editorial team

Formula

Available HELOC credit: Max Combined Loan-to-Value (CLTV): Max Total Debt = Home Value × LTV Limit Available HELOC: Available = Max Total Debt − Current Mortgage Balance Monthly payment during draw period (interest-only): Interest_only = Draw × (Annual Rate / 12) Monthly payment during repayment period (fully amortizing): M = Draw × [ r × (1 + r)^n ] / [ (1 + r)^n − 1 ] Where: r = Monthly rate (Annual rate ÷ 12) n = Repayment period in months Draw = Balance at end of draw period (assuming no paydown during draw) Example: $450,000 home, $250,000 mortgage, 85% LTV cap Max total debt: 450,000 × 0.85 = $382,500 Available HELOC: 382,500 − 250,000 = $132,500 Drawing $50,000 at 8.5% rate, 10-year draw / 20-year repayment: Interest-only payment during draw: 50,000 × 0.085 / 12 ≈ $354/mo Fully amortizing payment during repayment: 50,000 × [0.00708 × 1.00708^240] / [1.00708^240 − 1] ≈ $434/mo Payment shock at transition: $354 → $434 (+$80/mo). Manageable in this scenario, but at higher balances or shorter repayment periods, the increase can be much larger.

How to use this calculator

  1. Enter your home's current market value. Lenders typically use an appraisal or AVM (automated valuation) at application time; for planning, use a reasonable estimate from a recent comparable sale or Zillow/Redfin Zestimate.
  2. Enter your current mortgage balance — what you owe today, not the original loan amount.
  3. Enter the maximum combined LTV (CLTV) the lender allows. Most lenders cap at 80–85% for HELOCs. A few will go to 90% on smaller balances or higher credit scores; some cap at 75% on investment properties.
  4. Enter the amount you plan to draw. This can be the full available HELOC, or a smaller amount tailored to a specific purpose (renovation, debt consolidation, business investment).
  5. Enter the interest rate. HELOCs are usually variable — current quoted rates run roughly 8–10% in moderate-rate environments. Some lenders offer fixed-rate conversion options on portions of the balance.
  6. Enter the draw period (typically 10 years) and repayment period (typically 10–20 years).
  7. Compare interest-only draw-period payment to fully-amortizing repayment-period payment. The latter is what you should stress-test against your future budget — the draw period feels affordable; the repayment period reveals the true cost.
  8. If the repayment payment exceeds what you can sustainably afford, draw less or plan to pay down principal voluntarily during the draw period.

Worked examples

Renovation funding — small draw, manageable

$500,000 home, $300,000 mortgage, 85% CLTV cap → $125,000 HELOC available. Drawing $40,000 at 8.5%, 10-year draw / 20-year repayment. Draw-period payment (interest-only): $283/mo Repayment-period payment (full amortization): $347/mo Total interest paid over life: ≈ $43,400 Used for a $40,000 kitchen renovation, the after-renovation home is worth more than $500K, often by close to the renovation cost. Total interest of $43K on a 30-year ramp is meaningful — consider paying down faster.

Debt consolidation — large draw, payment shock at transition

$600,000 home, $200,000 mortgage, 80% CLTV cap → $280,000 HELOC available. Drawing $100,000 at 9.0% to consolidate credit card and personal loan debt. Draw period (10 years, interest only): $750/mo Repayment period (15 years): $1,015/mo Payment shock at year 10: +$265/mo Total interest over the life: ≈ $87,000. Compared to credit cards at 22%, this saves enormous interest. But the home is now collateral — missed payments can lead to foreclosure, unlike unsecured credit card default.

Maximum draw — payment shock could be severe

$700,000 home, $400,000 mortgage, 85% CLTV → $195,000 HELOC. Drawing $195,000 at 8.5%, 10-year draw / 10-year repayment (shorter). Draw period: $1,381/mo (interest only) Repayment period: $2,416/mo (full amortization) Payment shock: +$1,035/mo at year 10 That is a dramatic payment increase. A household able to handle $1,381 may not be able to handle $2,416. Always model the repayment-period payment, not the draw-period payment, when deciding whether to draw the full amount.

When to use this calculator

Use this calculator when considering a HELOC for home improvement, debt consolidation, education funding, business capital, or as a standby emergency reserve. The flexibility of a HELOC (only pay interest on what you use, redraw as needed) makes it well-suited to projects with uncertain or staged funding needs.

A HELOC is most appropriate when: (1) you have substantial home equity and a manageable existing mortgage, (2) the use of funds is for an appreciating or value-creating purpose (home improvement, debt consolidation at a lower rate, business investment), and (3) you have a clear plan for the repayment-period payment, not just the draw-period payment.

It is less appropriate when: (1) you might use it for ongoing discretionary spending (vacations, lifestyle), (2) home values are volatile and you could end up owing more than the home is worth, (3) you cannot reliably afford the repayment-period payment, or (4) you might lose the home to a missed payment — HELOC defaults can trigger foreclosure since the home is collateral.

Pair this calculator with the home-equity calculator (for lump-sum fixed-rate alternative), the mortgage-refinance calculator (sometimes a cash-out refi is cheaper than a HELOC), the personal-loan calculator (for unsecured comparison), and the debt-consolidation calculator if the purpose is to consolidate high-interest unsecured debt.

Tax note: under current law (TCJA, 2018–2025), HELOC interest is deductible only when the funds are used to "buy, build, or substantially improve" the home that secures the loan — not for general personal use. Always confirm with a tax professional.

Common mistakes to avoid

  • Treating the draw period's interest-only payment as the real cost. The true monthly cost is the fully-amortizing payment that kicks in once the draw period ends. Budget for that figure, not the lower interest-only number.
  • Ignoring variable-rate risk. Most HELOCs are tied to Prime, which moves with the Federal Reserve's policy rate. A rate that's 8.5% today could be 10–11% in two years and 6–7% in five years. Stress-test at 2–3% above current.
  • Drawing the full available limit reflexively. Just because you can borrow $150,000 doesn't mean you should. Larger balances at the end of the draw period mean larger payment shocks at transition.
  • Using HELOC funds for depreciating purchases (cars, vacations, consumer goods). The loan persists for 15–30 years; the value the money bought may be gone in 3–5. The mismatch creates long-term financial pressure with nothing left to show for it.
  • Forgetting that the home is collateral. Credit card default damages credit; HELOC default can trigger foreclosure. The lower rate comes at the cost of much higher consequence for missed payments.
  • Underestimating closing costs. HELOCs typically have $0–$1,500 in fees, but some lenders charge appraisals ($300–$800), title work ($300–$800), and recording fees. Read the disclosure carefully.

Frequently Asked Questions

Sources & further reading

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