🏠 HELOC Calculator: Estimate Your Home Equity Line of Credit
By Shihab Mia · Reviewed by ToolNimba Review Team, Personal finance reviewer · Updated 2026-07-26
This HELOC calculator gives an estimate for planning only and is not financial, lending, or tax advice. Actual credit limits, rates, fees, and payments depend on your lender, credit profile, and a property appraisal, so confirm every figure with a licensed lender before borrowing, and speak with a tax professional before assuming any interest is deductible.
Available credit
Payment estimate
Capped at your available credit.
A HELOC calculator tells you two things: how much credit a lender might extend against your home, and what the payment looks like in each phase of the loan. Enter your home value, your current mortgage balance, and the maximum combined loan-to-value (CLTV) your lender allows, and this tool returns your available credit instantly. It then estimates the interest-only payment during the draw period and the higher fully amortized payment once repayment begins, so you can see the full cost before you apply, not just the small number a lender advertises.
What is the HELOC Calculator?
A home equity line of credit, or HELOC, is a revolving credit line secured by the equity in your home, similar in structure to a credit card but backed by real property and usually offered at a much lower rate. This HELOC calculator works in two stages. First it sizes the line: lenders cap your total secured debt at a combined loan-to-value ratio, usually around 80% to 90% of the home value. Multiply the home value by that CLTV percentage, subtract whatever you still owe on the first mortgage, and the remainder is the equity you can borrow against. If the result is negative because your mortgage already uses more than the allowed share of value, the available credit is simply zero.
The second stage estimates the monthly cost, and this is where many borrowers get caught out. A HELOC has two distinct phases. During the draw period, often the first 5 to 10 years, you can borrow, repay, and re-borrow up to your limit, and most lenders only require an interest-only payment. That payment is small because it equals your current balance multiplied by the monthly rate (the APR divided by 1,200). It is tempting, but it never reduces what you owe. Some lenders instead require a small minimum principal payment, often around 1% to 2% of the balance, during the draw period; check your loan disclosure for the exact structure since it changes the true monthly cost.
When the draw period ends, the line enters the repayment period. You can no longer draw funds, and the outstanding balance is amortized, meaning each payment now covers both interest and principal so the loan is fully paid off by the end of the term. Because principal is added and the timeline is fixed, this payment is dramatically higher than the interest-only figure. This jump is called payment shock, and the HELOC calculator above shows both numbers side by side so you can plan for it before it arrives.
Lenders also underwrite HELOCs on your credit profile, not just your equity. Most want a credit score in at least the mid-600s, with the best rates and highest limits reserved for scores around 700 and above, plus a debt-to-income (DTI) ratio at or below roughly 43%, though strong-equity borrowers can sometimes go higher. Expect an appraisal, an annual or one-time fee in some cases, and possibly closing costs of a few hundred to a few thousand dollars, all of which add to the real cost of the line beyond the interest rate alone.
A HELOC is not the only way to tap home equity. A home equity loan gives you a lump sum at a fixed rate with a fixed payment from day one, which is easier to budget for but less flexible than a line of credit you draw as needed. A cash-out refinance replaces your entire first mortgage with a new, larger one, which can make sense if current rates are close to or below your existing mortgage rate but usually means higher closing costs and resets your mortgage term. Because most HELOCs carry a variable interest rate tied to the prime rate, your real payments move with the market. The estimate here uses the single APR you enter and assumes you draw the full amount at once, which is the conservative, worst-case view. Use it to compare lenders, to test how a rate increase would feel, and to decide whether the repayment-period payment fits comfortably inside your budget rather than just the easy interest-only number.
When to use it
- Estimating how much equity you can actually borrow before you apply, using your home value and mortgage balance.
- Seeing the gap between the low interest-only draw payment and the higher repayment-period payment so you can plan for payment shock.
- Comparing offers from different lenders by changing the CLTV limit and APR.
- Stress-testing your budget against a higher rate, since most HELOCs are variable.
- Deciding between a HELOC, a home equity loan, and a cash-out refinance by checking the monthly cost of each option.
- Planning a renovation, debt consolidation, or tuition payment funded by home equity, and checking whether the payment still fits your budget once repayment begins.
How to use the HELOC Calculator
- Enter your current home value (use a recent appraisal or a conservative estimate) and the balance still owed on your first mortgage.
- Set the maximum combined loan-to-value (CLTV) your lender allows. 85% is a common default; some allow 80% or 90%.
- Type the amount you plan to draw and the interest rate (APR) the lender quoted you.
- Set the interest-only draw period and the repayment period in years to match the loan terms.
- Read the available credit, the interest-only payment during the draw period, and the higher amortized payment for the repayment period.
- Re-run the numbers at a higher APR to see how a rate increase would affect your payment, since most HELOCs are variable.
Formula & method
Worked examples
Your home is worth $450,000, you owe $250,000 on the mortgage, and the lender allows an 85% CLTV.
- Maximum total secured debt = 450,000 × 0.85 = 382,500
- Subtract the existing mortgage = 382,500 − 250,000 = 132,500
- The result is positive, so this is your available credit
Result: Available HELOC credit = $132,500
You draw $100,000 at an 8.5% APR with a 10-year interest-only draw period, then a 20-year repayment period.
- Monthly rate i = 8.5 ÷ 1200 = 0.0070833
- Interest-only payment = 100,000 × 0.0070833 = 708.33 per month during the draw period
- For repayment, n = 20 × 12 = 240 months
- Payment = 100,000 × [0.0070833 × 1.0070833^240] ÷ [1.0070833^240 − 1]
Result: Interest-only payment about $708.33/mo, repayment payment about $867.82/mo
A borrower with a $600,000 home and a $480,000 mortgage checks a lender that caps CLTV at 80%.
- Maximum total secured debt = 600,000 × 0.80 = 480,000
- Subtract the existing mortgage = 480,000 − 480,000 = 0
- The mortgage already uses the full allowed share of value
Result: Available HELOC credit = $0 at this lender; a higher CLTV limit or a smaller mortgage balance would be needed to qualify
Available HELOC credit on a $450,000 home at common CLTV limits
| CLTV limit | Max total debt | Less $250,000 mortgage | Available credit |
|---|---|---|---|
| 80% | $360,000 | $360,000 − $250,000 | $110,000 |
| 85% | $382,500 | $382,500 − $250,000 | $132,500 |
| 90% | $405,000 | $405,000 − $250,000 | $155,000 |
| 95% | $427,500 | $427,500 − $250,000 | $177,500 |
Interest-only vs repayment payment on a $100,000 balance (20-year repayment)
| APR | Interest-only payment | Repayment payment | Monthly increase |
|---|---|---|---|
| 6.0% | $500.00 | $716.43 | $216.43 |
| 7.5% | $625.00 | $805.59 | $180.59 |
| 8.5% | $708.33 | $867.82 | $159.49 |
| 10.0% | $833.33 | $965.02 | $131.69 |
HELOC vs home equity loan vs cash-out refinance
| Feature | HELOC | Home equity loan | Cash-out refinance |
|---|---|---|---|
| Funds | Draw as needed, revolving | Lump sum, one time | Lump sum, one time |
| Rate type | Usually variable | Usually fixed | Usually fixed |
| Early payment | Interest only (typical) | Principal and interest | Principal and interest |
| Replaces first mortgage | No, sits behind it | No, sits behind it | Yes, replaces it entirely |
| Best for | Ongoing or uncertain costs | One-time known expense | When current rates beat your existing mortgage rate |
Common mistakes to avoid
- Budgeting only for the interest-only payment. The low draw-period payment never reduces your balance. When repayment begins, the payment can jump by hundreds of dollars a month. Always check whether the repayment-period figure fits your budget, not just the easy interest-only number.
- Forgetting your first mortgage counts toward CLTV. A HELOC is limited by combined loan-to-value, so the lender adds your existing mortgage to the new line. If your mortgage already uses most of the allowed share of value, your available credit can be small or even zero.
- Assuming the rate is fixed. Most HELOCs carry a variable rate tied to the prime rate. The payment you see today can rise if rates climb. Re-run the calculator at a higher APR to see how much room you really have.
- Using an outdated or optimistic home value. Your available credit depends entirely on the appraised value. Guessing high inflates the result. Lenders order their own appraisal, so use a conservative, recent estimate when you plan.
- Ignoring fees and closing costs when comparing offers. Two lenders quoting the same APR can differ once you add an annual fee, an appraisal fee, or closing costs. Ask each lender for the full fee schedule, not just the headline rate, before comparing payments.
- Forgetting a HELOC is secured by your home. Because the line is secured by your property, missed payments put your home at risk of foreclosure, unlike an unsecured personal loan or credit card. Only draw what you can comfortably repay under the higher repayment-period payment, not just the interest-only one.
Glossary
- HELOC
- Home equity line of credit, a revolving credit line secured by the equity in your home that you can draw from, repay, and re-borrow.
- Combined loan-to-value (CLTV)
- The total of all loans secured by the home divided by its value, expressed as a percentage. Lenders cap a HELOC by this ratio.
- Draw period
- The early phase of a HELOC, often 5 to 10 years, when you can borrow against the line and usually pay interest only.
- Repayment period
- The phase after the draw period when you can no longer borrow and the balance is amortized into principal-and-interest payments.
- Interest-only payment
- A payment that covers only the interest on the current balance, equal to balance times the monthly rate, leaving the principal unchanged.
- Payment shock
- The sharp rise in the monthly payment when a HELOC moves from the interest-only draw period to the amortized repayment period.
- Debt-to-income ratio (DTI)
- Your total monthly debt payments divided by your gross monthly income, expressed as a percentage. Lenders use it alongside CLTV to decide how much HELOC you qualify for.
- Prime rate
- The benchmark interest rate banks use as a base for variable-rate products. Most HELOC rates are quoted as the prime rate plus a margin, so the payment moves when the prime rate changes.
Frequently asked questions
How much can I borrow with a HELOC?
Multiply your home value by the lender CLTV limit (commonly 80% to 90%), then subtract your current mortgage balance. For a $450,000 home at 85% CLTV with a $250,000 mortgage, that is 382,500 minus 250,000 = $132,500 of available credit. If the result is negative, you have no borrowable equity.
How is a HELOC payment calculated?
There are two payments. During the draw period it is usually interest only: balance times the APR divided by 1,200. During repayment the balance is amortized, so the payment also includes principal and is calculated with the standard loan formula over the repayment term. The repayment payment is always higher.
What is the difference between the draw period and the repayment period?
In the draw period (often 5 to 10 years) you can borrow up to your limit and usually pay only interest. When it ends you enter the repayment period: no new borrowing, and the balance is amortized into full principal-and-interest payments until the loan is paid off.
Why does my HELOC payment jump after the draw period?
During the draw period you pay interest only, which never touches the principal. When repayment starts, the entire balance must be paid off over a fixed number of years, so each payment now includes principal. This payment shock can add hundreds of dollars a month, which is why this calculator shows both figures.
What CLTV do HELOC lenders allow?
Most lenders cap combined loan-to-value at 80% to 90% of the home value, though some go to 85% or higher for strong borrowers. A lower CLTV limit means less available credit. This calculator defaults to 85%, but you can change it to match your lender quote.
Is the interest rate on a HELOC fixed or variable?
Most HELOCs carry a variable rate tied to the prime rate, so your payment can rise or fall over time. This calculator uses the single APR you enter for a clear snapshot. To see your risk, re-run it with a higher rate to model what a rate increase would do to your payment.
What credit score and DTI do I need for a HELOC?
Most lenders look for a credit score of at least the mid-600s, with scores around 700 or higher qualifying for the best rates and limits, plus a debt-to-income ratio at or below roughly 43%. Requirements vary by lender, and strong home equity can sometimes offset a higher DTI.
Is HELOC interest tax deductible?
Under current federal rules, HELOC interest is deductible only if the funds are used to buy, build, or substantially improve the home that secures the loan, and only within the overall mortgage debt limits set by the IRS. Interest on funds used for other purposes, like paying off credit cards, generally is not deductible. Check IRS Publication 936 and confirm with a tax professional for your situation.
What is the difference between a HELOC and a home equity loan?
A HELOC is a revolving line you draw from as needed, usually at a variable rate with an interest-only draw period. A home equity loan gives you a single lump sum upfront at a fixed rate with a fixed principal-and-interest payment from day one. A HELOC suits ongoing or uncertain expenses; a home equity loan suits a single known cost.
What happens to a HELOC if I sell my home?
Any outstanding HELOC balance must be paid off at closing from the sale proceeds, the same way your first mortgage is paid off, since the line is secured by the property. If the combined mortgage and HELOC balance exceeds what the home sells for, you would need to cover the shortfall to close the sale.
Sources
- Home Equity Line of Credit (HELOC) , Consumer Financial Protection Bureau
- Home Equity Line of Credit (HELOC) , Investopedia
- Publication 936, Home Mortgage Interest Deduction , Internal Revenue Service