How our refinance calculators work

The formulas

P is the loan principal; r is the annual interest rate divided by 100 and then by 12; n is the loan term in years multiplied by 12. For your existing loan, n uses the years left on that loan.

Monthly payment = P × r / (1 − (1 + r)^(-n))
At 0% interest: monthly payment = P / n
Existing payment = payment on current balance at current rate over years left
New principal = current loan balance + cash-out amount
Monthly savings = existing monthly payment − new monthly payment
Total interest = monthly payment × number of months − principal
Existing remaining interest = existing payment × months left − current balance
Lifetime interest savings = existing remaining interest − new total interest
Closing costs = new principal × 0.02
Break-even months = closing costs / monthly savings (rounded up)

Break-even is shown only when monthly savings are positive. Lifetime interest savings does not subtract closing costs. When monthly or lifetime savings are zero or negative, the calculator shows a dash rather than a positive savings amount.

Rate data

Our public benchmarks are Freddie Mac Primary Mortgage Market Survey (PMMS) weekly 30-year and 15-year fixed-rate averages. The daily refresh retrieves the latest observations into our rate table; it does not make a weekly survey a daily quote.

The 15-year term uses the 15-year average. The 20- and 30-year terms, FHA, VA, and cash-out defaults use the 30-year average as a starting point, not a program-specific offer. Actual offers vary by credit, loan-to-value (LTV), loan size, and program.

If an observation is more than 14 days old, we label it as the last known average and keep its date visible. If no rate is available, we do not invent a replacement. Optimal Blue indices are not used in the public calculator or displayed here.

Default assumptions

• Closing costs default to 2% of the new loan principal, including any cash-out amount. They are not added to the new balance or financed in the payment calculation.
• The starting loan balance is 70% of the page’s home-value estimate, rounded to the nearest $1,000. Pages without a localized value use a $400,000 home value. This is an editable starting estimate, not an LTV eligibility check.
• The new loan term starts at 30 years; available terms are 15, 20, and 30 years.
• The optional Years left on current loan input sets the remaining term of your existing loan. Your current payment and remaining interest are calculated on your current balance at your current rate over those remaining years. If you leave it blank, we assume the years left equal the selected new term.
• The existing interest rate starts at the 30-year PMMS average; replace it with your actual rate. The new rate is also editable; changing the term resets that new-rate override to the relevant PMMS benchmark.
• Cash-out starts at zero except on cash-out calculators, where it is enabled with a $25,000 starting amount. Cash-out increases the new principal.
• Payments include principal and interest only. Property taxes, homeowners insurance, HOA dues, PMI, FHA MIP, and VA funding fees are not included. Program fee information elsewhere on the site is not incorporated into these estimates.
• Rates are treated as fixed nominal interest rates, not an APR calculation. No adjustable-rate changes, extra payments, tax deductions, or changes in home value are modeled. Currency results are rounded to whole dollars.

Not a lender

reficalculator.com is not a lender, broker, or financial advisor. These estimates do not constitute a loan offer, approval, or commitment to lend. Consult a licensed mortgage professional before making financial decisions.

How lead sharing works

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