How to Use a Cash-Out Refinance Calculator

Give a cash-out refinance calculator a $400,000 house and a $240,000 mortgage balance and it will say that about $80,000 is available. It is right about the amount. It says nothing about the price. For a homeowner paying 4.5% on that balance, moving to a new loan near 7.5% raises the first year's interest bill by roughly $13,000. Measured against the cash actually received after closing costs, that is a cost of about 18% to 20% a year, which is not the 7.5% shown on the screen.

None of this makes the calculator useless. It means the calculator has to be read properly. It takes four inputs and applies one cap, and it leaves out one sum that decides the matter. What follows covers the inputs, runs the $400,000 example with rates as published on October 29, 2026, and shows how to do the missing sum by hand.

Every cash-out calculator rests on loan-to-value, or LTV: the new loan divided by the home's appraised value. Lenders cap it, and the cap decides the result. For a conventional loan on a one-unit primary residence the cap is 80%, so the owner keeps at least 20% equity after closing. For two-unit primary homes it falls to 75%, and for some multi-unit investment properties it is as low as 70%, according to AmeriSave's breakdown by loan type. FHA cash-out loans are also capped at 80%, down from 85% under a HUD Mortgagee Letter. VA loans can reach 100% under the program, though many lenders apply a 90% limit of their own. USDA loans do not allow cash-out refinancing at all. Texas caps every cash-out loan at 80%, VA included, under Section 50(a)(6) of its constitution.

The arithmetic is short. Home value times the cap gives the largest new loan. Subtract the payoff on the existing mortgage and any other liens, and what remains is the cash available before closing costs. On AmeriSave's example, a $300,000 home with a $180,000 balance at an 80% cap leaves $60,000.

Here the first surprise usually arrives. Equity and available cash are different numbers. Lower.com's illustration is a $500,000 home owing $300,000: about $200,000 of equity, but only about $100,000 can be borrowed, because the 80% cap holds back the first fifth of the home's value. A calculator that shows half the expected figure is not broken. It is applying the cap.

It costs nothing and takes perhaps half an hour, most of it spent finding statements. The inputs that matter are these:

Lenders also look at debt-to-income, or DTI: monthly debt payments, including the new mortgage's principal, interest, taxes and insurance, divided by gross monthly income. Most cap it around 43%. Under Fannie Mae's Selling Guide, a DTI above 45% on a Desktop Underwriter file requires six months of reserves. Few calculators ask about income, so this limit catches people at application.

The example is hypothetical: a $400,000 single-family primary residence, a conventional loan, a $240,000 balance on an existing 4.5% mortgage with 25 years left, and a borrower with good credit. The steps below follow the order most lender tools use.

There is a fair objection, and it deserves a full hearing. The year-one figure overstates the cost over time: the added interest shrinks as the loan is paid down, a fixed rate is locked for 30 years while second-lien pricing can change, and the comparison assumes the alternative is available at a known rate. All true. It also depends heavily on the old rate. Rerun it for a borrower already paying 7.25% and repricing $240,000 by a quarter point costs about $600 a year. Add $6,000 of interest on the new $80,000 and the cash costs roughly 9%, close to the headline rate. The calculation does not condemn cash-out refinancing. It sorts borrowers. For anyone holding a rate well below the market, it says the refinance is mostly a way to give up that rate, and that cost should be counted against the cash.

The break-even check follows the same logic. Take the extra upfront cost of one option over the other and divide it by the monthly saving it buys. The answer is the number of months until the cheaper-looking option actually is cheaper. If that is longer than the owner expects to keep the loan, the cheaper-looking option loses. For the formula itself set out line by line, the blog's walkthrough of the cash-out math has it.

Treating equity as cash. The sign: the calculator's figure is well below the home value minus the balance. That is the 80% cap at work, not an error. The fix is to plan around value times the cap, minus the payoff.

An optimistic home value. The sign is an appraisal that comes in below the estimate, which shrinks the maximum loan and the cash with it. Entering a value 5% below the best guess shows how much room there is before the plan stops working.

Rolling in closing costs without pricing them. Financing the fees keeps cash out of pocket today and costs more later. The Mortgage Reports estimates that rolling $10,000 of costs into a 30-year loan at 4% adds about $19,100 in interest over its life, and the figure is higher at today's rates. Lower.com also notes that prepaid interest and escrow deposits can reduce net cash, and that an FHA upfront premium or VA funding fee, which runs from 0.5% to 3.3% of the loan, adds to the balance without adding to the cash. The sign is a net cash figure several thousand dollars below gross cash. The fix is to run the calculator twice, once with the costs paid in cash and once with them financed.

Reading the payment as the answer. The sign is a decision made on whether the new monthly payment feels affordable. Affordability is a lender's question. Cost is the borrower's, and it needs the sum in the table above.

Once the effective cost is known, the next question is what the alternative costs. If the old rate is well below today's, that alternative is usually a HELOC or home equity loan sitting behind the existing mortgage, and the comparison needs a real second-lien quote and its fees. For a borrower whose first mortgage is already priced near the market, the question becomes whether a plain rate-and-term refinance still pencils out alongside the cash.

Lender pricing varies more than the averages suggest. Using 2024 HMDA data, The Mortgage Reports ranked 25 lenders' average 30-year cash-out rates from 6.01% at Navy Federal to 8.07% at AmeriSave. A two-point spread on $320,000 is worth more than any calculator setting, so the estimate becomes useful only once there are several quotes on the same loan amount, the same day, with the closing costs listed.