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HELOC Calculator — How Much Can You Borrow?

See how much you can borrow against your home. This calculator uses the lender combined loan-to-value (CLTV) rule — total of all loans on the home capped at a share of its value (often 85%) — to turn your home value and mortgage balance into your available home-equity line, alongside your current equity and LTV. It can also estimate the interest-only draw payment and the amortizing repayment payment on an amount you draw.

Your numbers

$

Estimated current market value of your home.

$

What you still owe on your first mortgage (0 if paid off).

%

Combined loan-to-value cap, usually 80%–90%.

Optional: payment estimate

$

How much you plan to borrow from the line (0 to skip).

%

The rate on the line, e.g. 8.5. HELOC rates are usually variable.

yr

Amortizing repayment phase after the draw period, often 20 years.

Results

Available to borrow$125,000.00

Your equity

Current equity$200,000.00
Current mortgage LTV60%
Equity as % of value40%
Max total debt (85% CLTV)$425,000.00

Payment estimate on $50,000.00 drawn

Interest-only (draw period)$354.17
Amortizing (20-yr repayment)$433.91

CLTV caps and rates vary by lender, and HELOC rates are usually variable. This excludes credit-score and income qualification. Educational estimate only — not an offer or financial advice.

Your home equity is the part of your home you actually own: its current market value minus what you still owe on the mortgage. A HELOC (home equity line of credit) or a home equity loan lets you borrow against that equity — but not all of it. Lenders cap how much you can borrow using the combined loan-to-value (CLTV) rule, and that cap is what this calculator solves for.

Equity, LTV, and CLTV

Three numbers describe where you stand:

  • Equity — home value minus mortgage balance. It’s the dollar value of the slice you own.
  • LTV (loan-to-value) — your mortgage balance ÷ home value. The lower it is, the more equity you have.
  • CLTV (combined loan-to-value) — the total of all loans on the home (your mortgage plus a new HELOC) ÷ home value. This is the one a lender checks when approving a second loan, because the new line stacks on top of your mortgage.

The available line is simply the CLTV cap turned into dollars, minus what your mortgage already uses: available = (home value × CLTV cap) − mortgage balance, never less than zero.

The draw period vs. the repayment period

A HELOC usually has two phases. During the draw period (commonly 10 years) you borrow as needed and typically pay only the interest on what you’ve drawn — a low payment, but the balance doesn’t shrink. When the draw period ends, the repayment period begins (often 20 years) and the payment jumps to a fully amortizing amount that pays off principal and interest. The calculator estimates both so the later increase isn’t a surprise. (A home equity loan skips the draw phase — it’s a lump sum on an amortizing schedule from day one.)

A worked example

Take the default scenario: a $500,000 home with a $300,000 mortgage and an 85% CLTV cap.

  • Current equity: $500,000 − $300,000 = $200,000
  • Current mortgage LTV: $300,000 ÷ $500,000 = 60%
  • Max total debt at 85% CLTV: $500,000 × 85% = $425,000
  • Available to borrow: $425,000 − $300,000 = $125,000

Now draw $50,000 at an 8.5% rate with a 20-year repayment phase:

  • Interest-only payment (draw period): $50,000 × (8.5% ÷ 12) ≈ $354.17/mo
  • Amortizing payment (repayment period): about $433.91/mo

If your mortgage already reaches the $425,000 cap, the available line is $0 — you have equity, but none of it is borrowable under the cap. And if you owe more than the home is worth (underwater), your equity is negative and you can’t borrow at all until values rise or you pay the balance down.

A note on what this is — and isn’t

This is an educational estimate, not an offer. CLTV caps and rates vary widely by lender — some allow only 80%, others up to 90% — so adjust the cap to your lender’s. HELOC rates are typically variable, meaning your real payment can change over time; the figures here assume a fixed rate for the estimate. The tool deliberately excludes the credit-score, income, and debt-to-income qualification a lender applies, so being under the CLTV cap doesn’t guarantee approval. Use the result as a starting point, then get an actual quote from a lender.

This is an educational tool, not financial advice. See our disclaimer.

Frequently asked questions

How much can I borrow on a HELOC?
Lenders cap the total of all loans secured by your home — your mortgage plus the new HELOC — at a combined loan-to-value (CLTV) ratio, commonly 85%. To find your available line, multiply your home value by the CLTV cap to get the maximum total debt, then subtract your current mortgage balance. For example, on a $500,000 home with a $300,000 mortgage at an 85% CLTV, the maximum total debt is $425,000, leaving about $125,000 you could borrow. If your mortgage is already at or above the cap, there is no available equity to borrow.
What is CLTV (combined loan-to-value)?
CLTV is the total of every loan secured by your home divided by the home’s value, expressed as a percentage. It differs from plain LTV, which counts only your first mortgage. A lender approving a HELOC looks at CLTV because the new line stacks on top of your existing mortgage: if your home is worth $500,000 and you owe $300,000, your current LTV is 60%, and borrowing up to an 85% CLTV would allow $125,000 more. Most lenders set the HELOC CLTV cap between 80% and 90%.
What is the difference between a HELOC and a home equity loan?
Both let you borrow against your equity and both are limited by the CLTV cap, so the borrowing-power math is the same. The difference is structure. A home equity loan is a lump sum at a fixed rate, repaid on a fixed amortizing schedule from day one — like a second mortgage. A HELOC is a revolving line of credit you draw from as needed, usually with a variable rate and an interest-only draw period (often 10 years) followed by an amortizing repayment period. This calculator shows both the interest-only draw payment and the amortizing repayment payment so you can compare.
How does the interest-only draw period work?
A HELOC typically has two phases. During the draw period (commonly 10 years) you can borrow against the line and are usually required to pay only the interest that accrues each month — that keeps the payment low, but the balance does not shrink. When the draw period ends, the repayment period begins (often 20 years) and your payment jumps to a fully amortizing amount that pays off both principal and interest. This calculator estimates both payments on an amount you enter so the eventual increase isn’t a surprise.
Can I borrow against my equity if I’m underwater or maxed out?
No. If your mortgage balance is already at or above the CLTV cap, there is no room left to borrow and this calculator shows $0 available rather than a negative number. If you are underwater — you owe more than the home is worth — you have negative equity and cannot take out a HELOC or home equity loan until values rise or you pay the balance down. The fix in both cases is more equity: a higher home value or a lower mortgage balance.

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