How to use the calculator
- Enter your existing mortgage details: current balance, interest rate, and years remaining.
- Enter the cash you want to access: this is the amount of equity you plan to pull from the home.
- Enter HELOC terms: the HELOC rate and repayment term. This tool models the HELOC as fully amortizing over that term.
- Enter refinance terms: the new refinance rate, refinance term, and any closing costs you plan to roll into the new loan balance.
- Click Calculate to see a side-by-side comparison. Use Copy Result if you want to paste the summary into an email, spreadsheet, or notes app.
Tip: if you are not sure about rates, run more than one scenario. Try a HELOC rate that is 1 to 2 percentage points higher than today's quote, or compare a 15-year refinance with a 30-year refinance. That kind of stress test often reveals whether an option is still affordable when conditions become less favorable.
The calculator uses the standard amortizing loan payment formula to estimate the monthly payment for principal , monthly interest rate , and number of monthly payments :
In plain language, the formula converts a loan balance into a level monthly payment by spreading principal and interest over a fixed number of months. The more months you use, the smaller the required payment tends to be, but the more time interest has to accumulate. That is why a long refinance can look comfortable from a monthly cash-flow perspective even when it produces more total interest over the full life of the loan.
- Existing mortgage in the HELOC scenario: your current mortgage continues unchanged. The calculator estimates the remaining payment and the remaining interest on that mortgage.
- HELOC: modeled as a separate amortizing loan for the cash amount over the HELOC term at the HELOC rate. The tool does not model a draw period, interest-only payments, or future rate changes.
- Cash-out refinance: modeled as a brand-new mortgage whose principal equals current balance + cash needed + closing costs, amortized over the refinance term at the refinance rate.
- Total interest: estimated as monthly payment multiplied by the number of months, minus principal. In the HELOC case, the mortgage interest and HELOC interest are added together.
These assumptions are intentionally simple so you can compare options quickly. Real lender offers may include points, lender credits, escrow changes, mortgage insurance, promotional HELOC rates, prepayment features, or rate adjustments. Use the calculator as a first-pass comparison and then confirm the exact structure with a lender before making a decision.
Worked example with sample numbers
Suppose you owe $250,000 on your mortgage at 4.00% with 20 years remaining, and you want to access $50,000 in cash. You are offered a HELOC at 8.00% for 10 years, or a cash-out refinance at 6.00% for 30 years with $5,000 in closing costs rolled into the loan.
With those inputs, a side-by-side estimate may look like this:
Illustrative comparison using sample figures| Option | Monthly Payment | Total Interest Paid |
|---|
| Existing + HELOC | $1,818 | $189,540 |
| Cash-Out Refi | $1,857 | $323,520 |
That example shows a common pattern. The HELOC path can sometimes keep lifetime interest lower because it preserves the progress you have already made on the original mortgage amortization schedule. A refinance, by contrast, may restart repayment over a much longer term. Even when the refinance rate is lower than the HELOC rate, resetting the clock can still cause total interest to rise because you are paying interest for more months.
A useful way to read the results is to separate cash-flow comfort from total cost. A longer refinance term can reduce the required payment, but it may increase total interest. A shorter term can do the opposite: higher payment now, lower interest over time. Neither choice is automatically right. It depends on whether you value breathing room in your monthly budget, long-run cost control, or flexibility in how and when you borrow.
Decision factors to consider beyond the math
The payment and interest totals matter, but they are not the whole story. Real borrowing decisions also depend on how stable you want the payment to be, how long you expect to keep the home, and how likely it is that you will need additional access to equity later.
1) Rate type and payment stability
Many HELOCs are variable-rate. That means the payment can rise if market rates rise. Some lenders offer fixed-rate conversion features on part of the balance, but the default structure is usually tied to an index plus a margin. A cash-out refinance is often fixed-rate, which can make budgeting simpler because the payment is predictable from month to month.
2) Term length and resetting the clock
If you have already paid your mortgage for years, refinancing into a fresh 30-year loan can extend the period you carry housing debt. Even with a lower rate, the longer timeline can increase total interest. On the other hand, a shorter refinance term may reduce total interest but force a higher payment. The calculator is useful here because it lets you test that tradeoff quickly.
3) Closing costs and break-even thinking
Refinances typically come with appraisal, title, lender, and recording fees. If you roll those costs into the loan, you may pay interest on them too. A HELOC often has lower upfront costs, but not always. Depending on the lender, there may still be annual fees, inactivity fees, minimum draw rules, or early-closure fees. Looking only at the headline interest rate can hide those details.
4) Flexibility of borrowing
A HELOC can be especially useful when you do not need all the cash at once. Think of a renovation paid in stages, or a project where contractor draws happen over several months. A cash-out refinance gives you a lump sum at closing. That can be convenient if the need is immediate and predictable, but less flexible if the project timeline is uncertain.
5) Time horizon and how long you expect to keep the home
If you expect to sell soon, large refinance closing costs may be hard to justify. If you plan to stay for many years, a refinance might be easier to manage and could be competitive depending on the rate and term. The calculator's total-interest result is most helpful for long-hold comparisons, while the monthly payment is often more relevant for short-term budget planning.
6) Risk and emergency planning
Both options are secured by your home. That means payment shock matters. Before you commit, run a conservative scenario where the HELOC rate is higher than expected, or where the refinance term is shorter than your first choice. If the resulting payment feels too tight, the safer decision may be to borrow less, wait, or choose the structure with more resilience in a downturn.
Practical questions (FAQ)
Is a HELOC payment always interest-only?
No. Many HELOCs have a draw period during which interest-only payments are allowed, followed by a repayment period. This calculator simplifies the HELOC as fully amortizing over the term you enter, which makes the comparison cleaner but less detailed than a real contract.
Does the calculator include taxes, insurance, or escrow?
No. The results focus on principal-and-interest payments and interest totals. Property taxes, homeowners insurance, HOA dues, and escrow changes can materially affect your real monthly housing cost, so treat the output as a loan comparison rather than a complete housing budget.
What if I plan to pay extra each month?
Extra payments can reduce interest meaningfully, especially on higher-rate debt. This tool assumes you make only the scheduled payment. You can still use it to compare baseline obligations and then decide which loan you would prepay more aggressively.
What if I want to borrow $0 and just compare rates?
You can enter $0 for cash needed if you want to compare the effect of replacing the mortgage. Keep in mind that the refinance amount will still include any closing costs you enter.
How should I think about total interest if I might sell or refinance again?
Full-term interest is useful for a long-run comparison, but if you expect to exit early, you may care more about short-run cash flow and upfront costs. In that case, compare the monthly payment, the closing costs, and your likely holding period. A lower payment today is not always cheaper overall, but it can still be the better fit for a short time horizon.
Limitations and important notes
- Variable-rate HELOCs: many HELOCs have variable rates and may include a draw period with interest-only payments. This calculator simplifies the HELOC as a fixed-rate, fully amortizing loan over the term entered.
- Fees and taxes: lender fees, points, appraisal costs, and potential tax effects are not modeled beyond the refinance closing-cost input.
- Mortgage insurance and underwriting: cash-out refinances may trigger mortgage insurance, different pricing tiers, or loan-to-value limits that are not checked here.
- Prepayments: extra payments can change interest totals materially. The tool assumes the calculated payment only.
- Decision context: the best option depends on your time horizon, your tolerance for payment changes, and whether you value one consolidated payment or flexible access to equity.
Because both options put your home at risk if payments cannot be made, conservative planning matters. Use the calculator to narrow the range of reasonable choices, then compare real lender disclosures side by side. A quote that looks attractive on rate alone can be much less compelling once term length, fees, and the amount borrowed are included in the picture.
