Mortgage Refinance Estimator: How Much You'd Realistically Save

Refinance calculators are good at the easy half of the question (what the new payment would be) and silent on the half that decides it. Two people with identical quotes get opposite answers depending on one number the calculator never asks for: how long you’ll keep the loan.

Use the estimator below for the arithmetic, then do the division that follows.

Estimate the two loans

Run it twice. First with your current balance, current rate and current payment. Then with the same balance at the quoted new rate and the payment that comes with it. The difference in the interest totals is your gross saving before costs.

For reference, the Freddie Mac survey put the 30-year fixed at 6.67% and the 15-year at 5.96% for the week ending 13 August 2026. Your quote will differ.

Then do the division the calculator skips

Closing costs ÷ monthly saving = months to break even.

$4,800 of costs against a $190 monthly saving is about 25 months. Stay five years and you’re clearly ahead. Sell in eighteen months and you paid $4,800 to save $3,420.

That single line is the decision. Everything else on this page is detail.

Three ways the estimate flatters itself

1. It usually ignores closing costs. Most calculators compare payments and stop. Costs are the whole reason break-even exists.

2. It assumes you keep the loan forever. Lifetime-saving figures assume you hold the new mortgage for its full term. Most people don’t. They move, or refinance again.

3. It hides the restarted clock. Refinancing a loan you’re eight years into back to a fresh 30-year term lowers the payment and adds eight years of interest. The monthly figure improves; the total can get worse.

The fix for the third one: refinance into a term matching your remaining years, or take the longer term and keep paying your current, higher payment. The second option gives you a lower required payment as a cushion while clearing the loan on the original schedule — the same structure that makes a 30-year paid like a 15-year attractive.

What to enter, precisely

Current balance, not the original loan amount.

Current rate and payment, principal and interest only. Leave taxes and insurance out of both sides, since they don’t change much and including them dilutes the comparison.

The quoted new rate, from an actual lender rather than an advertised headline. Advertised rates typically assume an excellent credit profile and sometimes include paid points.

Real closing costs, from a written estimate. This is the largest source of error in any refinance calculation, and it’s the one number people guess.

What no estimator can tell you

Whether you’ll qualify at the quoted rate. Pricing is banded by credit score, and on this size of loan the bands are worth thousands. Fixing the score first often beats shopping harder.

Whether you’ll still be here. The single biggest input, and it lives in your plans, not in the loan.

Whether a higher rate is still worth it. Removing mortgage insurance, escaping an adjustable rate, or consolidating expensive debt can all justify refinancing upward — the cases where that holds.

A short checklist before applying

• Get three quotes in a short window; mortgage inquiries in a tight period are generally treated as one event
• Compare total cost, not rate — a low rate bought with high fees is a longer break-even
• Ask each lender for the full closing-cost figure in writing
• Check whether the quote includes points
• Confirm the term you’re being offered, not just the rate

Run the numbers before you trust anyone’s headline rate. Today’s mortgage rates tell you what a fair quote looks like right now, and the mortgage guide is worth a look if any of the terms above weren’t familiar.