Guide · Refinance

How mortgage refinance math works

Educational guide · Updated · About 7 min read

Refinance math restarts amortization on your remaining balance (plus optional cash-out or rolled costs) at a new rate and term, then compares monthly payment and total interest to staying on the current path.

Two paths

  1. Keep the current balance, rate, and months left
  2. Start a new loan principal at the new rate and term

Sample

$300,000.00 · 6.5% with 300 months left → 5.5% for 360 months → monthly savings about $322.25. Open sample

Related

Frequently asked questions

What does a refinance calculator compare?

Usually the remaining path on your current rate/term versus a new fixed-rate loan, plus optional closing costs.

Sample monthly savings on $300k from 6.5% to 5.5%?

About $322.25 under Nestfigure’s stated sample.

Related tool

Compare refinance free

Current vs new payment and break-even.

Open refinance calculator

Sources linked above include U.S. government materials (for example CFPB, FDIC, NCUA, BLS, IRS) where noted. Sample math uses only labeled Nestfigure assumptions—not bank quotes, job offers, or personalized advice. Last reviewed: August 9, 2026.

YMYL notice: This site is for education only. It is not financial, tax, or investment advice. Nestfigure is not a bank, credit union, broker, investment adviser, or fiduciary. Product terms, rates, and penalties vary—always read your institution’s disclosures before acting. Calculator results are mathematical estimates, not bank quotes.