HELOC Calculator
A HELOC lets you borrow against your home's equity. Enter your home value, mortgage balance, and your lender's max combined loan-to-value to see how much you could borrow — then add a draw amount, rate, and your draw and repayment periods to see your interest-only payment now and the larger fully-amortizing payment when repayment begins. The calculator highlights the "payment shock" between the two phases so there are no surprises. (HELOC rates are usually variable; this is a fixed-rate estimate, not a forecast.)
Quick examples:
Your home's current market value (an estimate or recent appraisal).
The principal you still owe on your existing mortgage. Enter 0 if paid off.
The max % of your home's value all loans against it may total. Default 85% is an illustrative placeholder — enter your lender's actual cap.
How much you plan to borrow. Capped at your available line for the payment estimate.
Interest-only is the most common HELOC draw structure. Principal & interest pays the balance down during the draw, shrinking the payment shock.
HELOC Summary
Available Credit Line
Repayment Payment
Current Equity
Current LTV
Combined LTV After HELOC
Interest-Only Draw Payment
Total Interest (Overall)
HELOC rates are usually variable (typically Prime + a margin) and can rise or fall. This is a fixed-rate estimate, not a forecast, and assumes the full draw is outstanding for the whole draw period. Not financial advice.
Equity & CLTV Summary
| Home value | $400,000.00 |
| Current mortgage balance | $240,000.00 |
| Current equity | $160,000.00 |
| Current LTV | 60.00% |
| Max CLTV | 85.00% |
| Available credit line | $100,000.00 |
| Combined LTV after a $50,000.00 draw | 72.50% |
Payment Summary
| Phase | Monthly payment | Notes |
|---|---|---|
| Draw period (10 yr, interest-only) | $354.17 | On $50,000.00 at 8.50% |
| Repayment period (20 yr) | $433.91 | Amortizing $50,000.00 to $0 |
| Payment shock | +$79.74 | +22.52% when repayment begins |
Payment Over Time
The payment is flat during the interest-only draw period, then steps up to the higher amortizing payment when repayment begins. The dashed line tracks the outstanding balance declining to $0.
Yearly Repayment Schedule
Showing yearly rows because this schedule runs more than 60 months.
| Year | Payment | Principal | Interest | Balance |
|---|---|---|---|---|
| 1 | $5,206.94 | $995.11 | $4,211.82 | $49,004.89 |
| 2 | $5,206.94 | $1,083.07 | $4,123.87 | $47,921.81 |
| 3 | $5,206.94 | $1,178.81 | $4,028.13 | $46,743.00 |
| 4 | $5,206.94 | $1,283.00 | $3,923.94 | $45,460.00 |
| 5 | $5,206.94 | $1,396.41 | $3,810.53 | $44,063.59 |
| 6 | $5,206.94 | $1,519.84 | $3,687.10 | $42,543.75 |
| 7 | $5,206.94 | $1,654.18 | $3,552.76 | $40,889.57 |
| 8 | $5,206.94 | $1,800.39 | $3,406.55 | $39,089.18 |
| 9 | $5,206.94 | $1,959.53 | $3,247.41 | $37,129.65 |
| 10 | $5,206.94 | $2,132.74 | $3,074.20 | $34,996.91 |
| 11 | $5,206.94 | $2,321.25 | $2,885.69 | $32,675.66 |
| 12 | $5,206.94 | $2,526.43 | $2,680.51 | $30,149.23 |
| 13 | $5,206.94 | $2,749.74 | $2,457.20 | $27,399.49 |
| 14 | $5,206.94 | $2,992.79 | $2,214.15 | $24,406.70 |
| 15 | $5,206.94 | $3,257.33 | $1,949.61 | $21,149.37 |
| 16 | $5,206.94 | $3,545.25 | $1,661.69 | $17,604.12 |
| 17 | $5,206.94 | $3,858.62 | $1,348.32 | $13,745.50 |
| 18 | $5,206.94 | $4,199.68 | $1,007.26 | $9,545.82 |
| 19 | $5,206.94 | $4,570.90 | $636.04 | $4,974.92 |
| 20 | $5,206.94 | $4,974.92 | $232.02 | $0.00 |
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How This Calculator Works
A HELOC is a revolving line of credit secured by your home equity, and it works in two phases. During the draw period you can borrow up to your limit and typically pay interest only; during the repayment period you can no longer borrow and the outstanding balance amortizes into principal plus interest. This tool answers two questions at once: how much you could borrow against your equity, and what your payments would be in each phase — leading with the "payment shock" when repayment begins. Unlike the Refinance Calculator (which replaces your first mortgage with a larger cash-out loan) or the Mortgage Calculator (a single fully-amortizing loan from day one), a HELOC sits on top of your existing mortgage as a second, two-phase line.
Borrowing Power (Available Line)
availableLine = max(0, homeValue x CLTV − mortgageBalance)
Most lenders cap your total home-secured debt at a combined loan-to-value (CLTV) percentage — so your available line is your home value times that cap, minus what you still owe. The tool also shows your current equity (homeValue − mortgageBalance), your current LTV (mortgageBalance / homeValue), and the combined LTV after the HELOC ((mortgageBalance + draw) / homeValue) so you can see how close to the cap you would land. If your mortgage already hits the cap, the line clamps to $0.
Interest-Only Draw Payment
drawPayment = balance x (rate / 12)
In the default interest-only mode, each month you pay only the interest on the outstanding balance — nothing goes to principal, so the full draw carries into repayment. For example, $50,000 at 8.9% is roughly $50,000 x (0.089 / 12) ≈ $370.83 a month. That low payment is exactly why the later jump can be jarring. You can also switch the draw to principal & interest, which amortizes the balance during the draw period so it carries a smaller balance (and a smaller shock) into repayment.
Repayment Payment (Amortizing)
M = P x i(1+i)ⁿ / ((1+i)ⁿ − 1)
0% special case: M = P / n
When the draw period ends, the outstanding balance P amortizes over the repayment months n at monthly rate i (APR ÷ 12) using the standard PMT formula — the same engine behind our Amortization Calculator. The payment is level and pays the balance down to exactly $0 by the final month. When the rate is 0%, it switches to the special case to avoid dividing by zero.
Payment Shock & Total Interest
paymentShock = repaymentPayment − drawPayment
totalInterest = drawInterest + repaymentInterest
The headline teaching point is the payment shock — the dollar jump from the interest-only payment to the amortizing one, which in interest-only mode is often more than double. The tool also reports total interest for the draw period, the repayment period, and overall, assuming the full draw stays outstanding for the whole draw period. The repayment schedule reconciles to its interest total within a penny and forces the final balance to exactly $0 to absorb rounding drift.
Important: HELOC rates are usually variable
Real HELOCs almost always carry a variable interest rate — typically the Prime Rate plus a fixed margin — which can rise or fall over the life of the line as the index moves. To keep this estimate deterministic and shareable, the calculator deliberately models a single fixed rate that you enter. That means the numbers here are a fixed-rate estimate at this rate, not a forecast of where rates will go. This tool does not project rate changes, rate caps, or index movements. If rates climb, both your interest-only draw payment and your amortizing repayment payment would rise — so it is wise to re-run the estimate with a higher rate to stress-test your budget before committing.
Tips for Using a HELOC Wisely
Borrow Only What You Need
Just because the calculator shows a large available line doesn't mean you should draw it all. Because a HELOC is revolving, you can draw only the amount you actually need and leave the rest untapped — and you pay interest only on what you've borrowed. Enter a realistic draw amount rather than your full limit to see payments that match how you'd really use the line, and keep your combined LTV comfortably below the cap.
Plan for the Payment Shock
The most common HELOC surprise is the jump from an interest-only draw payment to a much larger amortizing repayment payment. Look at the repayment figure now, not just the comfortable draw payment, and make sure your budget can absorb the higher number years from now. If the shock looks steep, consider a longer repayment term, a smaller draw, or switching the draw to principal & interest so you pay the balance down early.
Watch the CLTV Cap
Your borrowing power is bounded by your lender's combined loan-to-value cap — the share of your home's value all loans against it may total. Enter your lender's actual cap (the 85% default is just an illustration) and watch the "combined LTV after HELOC" figure: drawing right up to the cap leaves no cushion if your home's value dips. Leaving headroom protects you if values fall or you need to borrow again later.
Mind Variable Rates — Stress-Test
Since real HELOC rates float with an index, the payment you see today can change. Re-run the calculator with a rate a few points higher than your lender's quote to see how much your interest-only and repayment payments could climb if rates rise. Building that buffer into your plan now means a rate increase won't catch your budget off guard later — treat the default rate as a placeholder and enter the rate you were actually quoted.
Common Ways People Use a HELOC Calculator
Fund a Home Renovation
RenovationA phased remodel — kitchen now, bathrooms next year — is a classic HELOC fit because you draw money as each stage bills you rather than borrowing one big lump sum up front. Enter your home value, mortgage balance, and CLTV cap to see your available line, then model a realistic draw to preview the interest-only payment during the project and the larger repayment payment afterward.
Consolidate Higher-Rate Debt
ConsolidationSome homeowners use home equity to pay off higher-rate balances, trading several payments for one lower-rate, home-secured line. Use the calculator to size the draw against your equity and compare the interest-only and repayment payments — and remember a HELOC puts your home on the line, so weigh that risk carefully against an unsecured option.
Keep an Emergency Backstop Line
BackstopBecause a HELOC is revolving, many people open one as a standby safety net — available if a big unexpected expense hits, costing nothing while undrawn. Model a small or zero draw to see your full available line and current equity, so you know exactly how much cushion you could tap and what carrying a balance would cost before you ever need it.
Cover a Big One-Time Expense
One-Time ExpenseTuition, a wedding, or a major medical bill can all be funded from home equity when other options are pricier. Enter the amount you plan to draw to see the interest-only payment now and the amortizing payment once the draw period ends, so you can decide whether the two-phase structure fits the expense and your repayment plan.
What This Calculator Assumes
To keep results deterministic and evergreen, the HELOC math rests on a few clear assumptions:
- •Full draw outstanding during the draw period: the payment estimate assumes you borrow your full draw amount up front and carry that balance for the whole draw period. Real HELOCs are revolving — you may draw and repay repeatedly — so your actual interest depends on your real balance over time. This keeps the estimate clear and shareable.
- •A single fixed rate, not a forecast: the rate is treated as fixed for the whole line for estimation, even though real HELOCs are variable (typically Prime + a margin). Results are an at-this-rate estimate, not a projection of where rates will go. Interest accrues monthly at APR ÷ 12, and the repayment balance amortizes to exactly $0 at the final scheduled payment.
- •No taxes, fees, or closing costs: no annual or maintenance fees, no draw fees, no closing costs, and no minimum-draw requirements are modeled. The home-equity interest deduction is described conceptually only — the tool computes no tax benefit.
- •No credit-score or income qualification: the available line uses the CLTV cap you enter and does not consider your credit score, income, DTI, or property type. It is an equity-based maximum, not a lender guarantee or approval estimate. Default rates, terms, and the 85% CLTV cap are plain illustrative placeholders, not sourced or maintained figures.
Disclaimer: This tool provides estimates for personal planning and is not financial, tax, or lending advice. Actual borrowing power, rates, and payments depend on your lender, your credit and income, your specific loan terms, and any fees in your agreement — and because HELOC rates are variable, your real payments can change over time. Confirm the details with your lender and consult a qualified professional before borrowing against your home.
Frequently Asked Questions
What is a HELOC and how does it work?
A HELOC (home equity line of credit) is a revolving line of credit secured by the equity in your home — similar to a credit card, but backed by your house and usually at a lower rate. It has two phases: a draw period (often 10 years) when you can borrow up to your credit limit and typically pay interest only on what you've used, and a repayment period (often 10-20 years) when you can no longer borrow and the outstanding balance is paid off in monthly principal-and-interest installments. Because it's revolving, you can borrow, repay, and borrow again during the draw period up to your limit. This calculator estimates both how large your line could be and what your payments would look like in each phase.
How much can I borrow with a HELOC?
Most lenders let your total home-secured debt reach a combined loan-to-value (CLTV) cap — commonly around 80-85% of your home's value — so your available line is roughly your home value times that cap, minus what you still owe on your mortgage. For example, on a $400,000 home with a $240,000 mortgage and an 85% cap, you could borrow up to $400,000 x 0.85 - $240,000 = $100,000. The actual amount also depends on your credit, income, and the lender's rules, which this tool doesn't judge — enter your lender's CLTV cap to see your equity-based maximum. If your mortgage already exceeds the cap, there's no available line.
What's the difference between the draw period and the repayment period?
The draw period is the borrowing phase: for a set number of years (often up to 10) you can take money from the line as you need it, and many HELOCs only require interest payments during this time. The repayment period begins when the draw period ends — you can no longer borrow, and whatever balance is outstanding gets amortized into fixed monthly payments of principal and interest over the remaining term. The shift matters a lot for your budget, because an interest-only payment can be far smaller than the later principal-and-interest payment. This calculator shows both payments side by side.
What is HELOC "payment shock"?
Payment shock is the jump in your monthly payment when the draw period ends and the repayment period begins. During the draw period you might pay only interest (say, $370 a month on a $50,000 balance), but once repayment starts you have to pay down the principal too, which can push the payment to $600+ a month — often more than double. The shorter your repayment term and the larger your balance, the bigger the shock. This calculator highlights the exact dollar increase and charts the step-up so you can plan for it before it happens.
Why are HELOC rates variable, and how does that affect this estimate?
Most HELOCs carry a variable interest rate, usually tied to the Prime Rate plus a fixed margin, so your rate — and your payment — can rise or fall over the life of the line as the index moves. To keep the estimate clear and shareable, this calculator uses a single fixed rate that you enter, which means it's a snapshot, not a forecast of where rates will go. If rates rise during your draw period, your interest-only payment increases; if they rise during repayment, your amortizing payment increases too. Treat the numbers here as an at-this-rate estimate and stress-test it by entering a higher rate.
How is the interest-only draw payment calculated?
During an interest-only draw period, your monthly payment is simply the outstanding balance times the monthly interest rate (the annual rate divided by 12). For example, $50,000 borrowed at an 8.9% annual rate is $50,000 x (0.089 / 12), about $370.83 per month, and because you're not paying down principal, the balance stays the same until the repayment period. That's why interest-only payments feel affordable but don't reduce what you owe. This calculator assumes your full draw amount is outstanding for the whole draw period to give a clear, deterministic estimate.
How is the repayment-period payment calculated?
When repayment begins, the outstanding balance is amortized — paid off in equal monthly installments of principal and interest — over the repayment term using the standard loan formula M = P x i(1+i)^n / ((1+i)^n - 1), where P is the balance, i is the monthly rate, and n is the number of repayment months. At a 0% rate the payment is simply the balance divided by the number of months. The result is a higher, level payment that pays the balance down to exactly $0 by the end of the term. This calculator shows that payment, the total interest you'd pay during repayment, and a month-by-month schedule.
What's the difference between a HELOC and a home equity loan?
A home equity loan is a lump sum you receive all at once and repay in fixed monthly payments at a fixed rate from day one — predictable, but you take the whole amount immediately whether you need it or not. A HELOC is a revolving line you can draw on as needed, usually at a variable rate, often with an interest-only draw period followed by a repayment period. A home equity loan suits a known, one-time expense; a HELOC suits ongoing or uncertain needs (like a phased renovation) where you want flexibility. This calculator models the HELOC structure specifically, including the two-phase payment pattern a home equity loan doesn't have.
HELOC vs cash-out refinance — which should I consider?
A cash-out refinance replaces your existing mortgage with a new, larger one and gives you the difference in cash, so you end up with a single new loan (and new rate and closing costs) covering both your old balance and the cash you took out. A HELOC leaves your first mortgage untouched and adds a second, revolving line on top of it — useful if your existing mortgage rate is low and you don't want to lose it. Cash-out refis are usually fixed-rate; HELOCs are usually variable with the two-phase structure. Use our Refinance Calculator to model a cash-out-style new loan, and this HELOC Calculator to model a second line against your equity.
Is HELOC interest tax deductible?
It depends on how you use the money, not on what the loan is called. Under current IRS rules, interest on a HELOC (and home equity loans and cash-out refinances) is generally deductible only when the funds are used to buy, build, or substantially improve the home that secures the loan — using it for debt consolidation, tuition, or a car typically isn't deductible. There are also overall mortgage-debt limits, and the rules have changed over time and can change again, so this is general information, not tax advice. This calculator does not compute any tax benefit; consult a tax professional for your situation.
What if I owe more than my home is worth, or my mortgage already hits the CLTV cap?
If your mortgage balance is at or above your home's value times the CLTV cap, your available line is $0 — there's no equity left to borrow against within the limit, and the calculator will tell you so rather than show a negative number. If you owe more than the home is worth (you're "underwater"), your equity is negative and a HELOC generally isn't available. In both cases you'd need your home value to rise or your mortgage balance to fall before a HELOC becomes possible. The calculator clamps these situations to $0 and shows a clear message instead of an error.
Can I share or save my HELOC estimate?
Yes. Every input is stored in the page's URL (compressed), so you can copy the link to share an exact scenario or bookmark it to return later — reloading restores the same numbers. You can also export a PDF of your full borrowing-power and payment summary. None of the major bank or comparison-site HELOC calculators offer link sharing or PDF export.