Mortgage Refinance Calculator

Calculations use standard amortizing loan formulas for periodic payment and logarithmic solution for number of periods when extra principal payments reduce the payoff time. Periodic rates equal annual rate divided by payments per year (12, 26, or 52).

We follow best practices for numeric stability and disclosure: rounding is applied only to displayed results; internal calculations use full precision. For data handling and security, implementations should follow NIST guidance for cryptography and secure storage, ISO 27001 for information security management, and IEEE recommendations for software quality and transparency.

This tool is an estimator and not an offer. Validate results with lender quotes and loan documents. See accuracy and caveats below.

Use this calculator to estimate the financial effect of refinancing and switching payment frequency. It highlights changes in per‑period payments, total interest, payoff time and estimated break‑even.

Always confirm estimates with lender disclosures and consider non‑modeled items such as escrow changes, taxes, insurance, and potential change in APR due to fees or rate structure.

Example: $300,000 balance, current rate 3.5% with 25 years left, refinance to 3.0% for 30 years with $3,000 fees and bi‑weekly payments. The tool compares scheduled payments, any reduction in total interest, and how many periods until the $3,000 is recouped.

Bi‑weekly payments accelerate principal reduction because there are 26 half‑payments per year; the effective annual payment amount and timing differ from 12 equal monthly payments. This calculator models those periodic differences directly by using 26 periods per year.