HELOC Calculator
On a $400,000 home with a $250,000 mortgage and an 85% CLTV limit, you could have up to $90,000 of credit line. Drawing $50,000 at 8.00% costs $333.33 a month interest-only, then $418.22 a month over 20 years.
Your home and line
Everything stays in your browser. The example is a $400,000 home with a $250,000 mortgage; replace it with your own numbers.
Your result
Your line could be up to $90,000. Drawing $50,000 at 8.00% costs $333.33 a month interest-only, then $418.22 a month for 20 years, with $90,373 of interest in total.
- Home equity
- $150,000
- Combined LTV after the draw
- 75.0%
- Rate (prime + margin)
- 8.00%
- Draw period payment
- $333.33
- Interest only, per month
- Repayment period payment
- $418.22
- Principal and interest, per month
- Total interest
- $90,373
- $40,000 draw + $50,373 repayment
Convention: one draw at the start, the rate held constant for the whole loan, no fees, interest-only payments during the draw period.
How it is calculated
- Line available = home value x max combined LTV - mortgage balance, never below zero.
- Rate = prime rate + margin. Both are inputs and the rate is held constant.
- Draw period payment = draw amount x rate / 12 (interest only).
- Repayment payment = the standard loan formula on the draw amount, at that rate, over the repayment years.
- Total interest = interest-only payments over the draw period + repayment payments - the draw amount.
Prime reference: the Federal Reserve H.15 release of October 26, 2026 shows a bank prime loan rate of 7.00% for October 23, 2026. It is a reference for the input, not the rate a lender will give you. The 85% CLTV limit and the 1.00% margin are examples, not rules.
- What is a home equity line of credit (HELOC)? (CFPB): “allows you to borrow repeatedly against your home equity”. Read 2026-10-27.
- CFPB, draw period: “The draw period could last 10 years, for example.”. Read 2026-10-27.
- CFPB, repayment period: “often over ten or 20 years”. Read 2026-10-27.
- CFPB, rate type: “HELOCs usually have a variable interest rate”. Read 2026-10-27.
- CFPB, lender can freeze the line: “freeze your ability to take out additional funds”. Read 2026-10-27.
- Federal Reserve H.15 Selected Interest Rates: “Bank prime loan”. Read 2026-10-27.
HELOC questions
How much can I borrow with a HELOC?
Lenders set a maximum combined loan-to-value (CLTV), the mortgage plus the HELOC as a share of the home value. The line is home value times that limit, minus your mortgage balance. With a $400,000 home, a $250,000 mortgage and an 85% limit, that is $90,000. The 85% is an example of a common lender limit, not a rule: each lender sets its own, so enter the one in your offer.
How is a HELOC payment calculated?
During the draw period many HELOCs ask only for interest on what you owe. Here that is the balance times the annual rate divided by 12: $333.33 on $50,000 at 8.00%. In the repayment period the balance is paid off over a fixed term, which at the same rate over 20 years is $418.22 a month. The CFPB notes that monthly payments are often significantly higher once repayment starts.
What interest rate will I pay on a HELOC?
The CFPB says HELOCs usually have a variable rate, so your payment can change. Many lenders quote it as an index plus a margin. This page lets you enter both: the bank prime loan rate was 7.00% for October 23, 2026 in the Federal Reserve's H.15 release of October 26, 2026, and the margin comes from your lender's offer. Your lender may use a different index, so treat prime as a reference, not as your rate. The calculator holds the rate constant for the whole loan.
How long are the draw and repayment periods?
The CFPB gives a draw period of 10 years as an example and says repayment often runs over ten or 20 years. Your agreement sets the real terms. The defaults here are 10 and 20 years and you can change both.
Can a lender reduce or freeze my line?
Yes. The CFPB says that if your home value drops significantly the lender may not allow more credit, and it may freeze your ability to take out funds if it doubts you can pay. The available line shown here is an estimate, not a commitment.
Related: the extra mortgage payment calculator and the rent vs buy calculator.
This is an educational tool, not financial or lending advice. It leaves out fees, closing costs, rate caps, minimum payments and the lender's own underwriting. Your home secures a HELOC, so missing payments puts it at risk.