The Refinance Calculator compares a current loan with a new loan to show monthly payment change, the months needed to recover closing costs, and estimated lifetime interest savings. Enter the remaining balance, current rate and term, the new rate and term, and closing costs, and the Refinance Calculator returns the payment delta, break-even month, and interest comparison under those assumptions.
A lower rate does not automatically mean a better deal. Upfront costs, a longer term that restarts amortization, and how long the borrower keeps the loan can erase the headline savings. State those assumptions beside every result.
*These results are estimates for information only, not financial, lending, or tax advice. Break-even and lifetime savings depend on the rate, term, closing costs, remaining balance, and how long the loan is kept; change those inputs and the decision can reverse.*
Decide whether to refinance
The Refinance Calculator decides whether refinancing is worth pursuing by weighing monthly savings against closing costs and total interest over the remaining life of each loan. The decision is whether break-even arrives before the planned move or payoff date, and whether lifetime interest still falls after costs.
Monthly savings alone is incomplete. Saving $150 per month looks strong until $3,600 in closing costs implies a 24-month wait to break even. If the home will be sold in 12 months, that refinance loses money on costs even though the new payment is lower. The Refinance Calculator puts payment, break-even, and lifetime interest on one screen so the timing question is explicit.
Taxes, points, cash-out amounts, and credit changes can alter the true cost. Model the loan terms that will actually close.
Compare the new and old payments
The Refinance Calculator compares the new and old monthly payments by amortizing each loan at its own interest rate and remaining or reset term. Monthly savings equals the old payment minus the new payment when the proposed payment is lower.
Payment for a fixed-rate amortizing loan follows the standard mortgage formula from principal, periodic rate, and number of payments. Example path: if the current payment is $1,850 and the refinanced payment is $1,700, monthly savings = 1,850 - 1,700 = $150. If the new term is longer, the payment can fall even when total interest rises, because the balance is spread over more months. The Refinance Calculator shows both payments and the signed monthly difference so a payment cut is never mistaken for an interest win without checking the schedule.
Escrow for tax and insurance can change at refinance. Compare principal-and-interest figures on the same basis, then layer escrow separately if needed.
Find the break-even month
The Refinance Calculator finds the break-even month by dividing total closing costs by the monthly payment savings. Break-even is how many months the lower payment must run before cumulative savings equal what was paid in cash to close the new loan.
Break-even months = closing costs / monthly savings. With $3,600 closing costs and $150 monthly savings, break-even = 3,600 / 150 = 24 months. Keep the loan past month 24 and the cumulative payment savings exceed closing costs (ignoring time value of money in the simple form). Leave before month 24 and the refinance has not yet paid for itself on that measure.
When monthly savings is zero or negative, break-even does not exist in the usual sense; the new loan costs more each month. The Refinance Calculator should flag that case instead of dividing by zero. Discounting savings at an opportunity rate makes break-even slightly longer; the simple ratio is the transparent starting point.
See your lifetime savings
The Refinance Calculator estimates lifetime savings as remaining interest on the old loan minus interest on the new loan, minus closing costs. Lifetime savings answers whether the refinance reduces total interest cost after paying to close, assuming both loans run on the schedules entered.
Amortize the old loan from today's balance through its remaining term; sum interest. Amortize the new loan from the same starting balance (plus any financed costs if those are rolled in) through its term; sum interest. Lifetime savings ~= old remaining interest - new total interest - closing costs paid in cash. Example shape: if old remaining interest is $120,000, new total interest is $95,000, and cash closing costs are $3,600, estimated savings are 120,000 - 95,000 - 3,600 = $21,400 under those schedules.
Extending the term can cut the payment and still raise total interest. The Refinance Calculator surfaces that tradeoff when the new term is longer than the old remaining term. Recalculate if the borrower will prepay early; lifetime figures assume the paths entered.
Frequently asked questions
How do you calculate refinance monthly savings?
Monthly savings is the old principal-and-interest payment minus the new payment. The Refinance Calculator amortizes both loans to get those payments. An old payment of $1,850 and a new payment of $1,700 save $150 per month.
How is the refinance break-even month calculated?
Break-even months equal closing costs divided by monthly savings. The Refinance Calculator uses that ratio. Costs of $3,600 with $150 saved per month break even in 24 months.
What counts as lifetime savings when refinancing?
Lifetime savings compares remaining interest on the old loan with interest on the new loan, then subtracts closing costs. The Refinance Calculator estimates that figure from the amortization schedules entered. Early payoff changes the result.
Does a lower payment always mean a good refinance?
No. A longer term can lower the payment while increasing total interest, and closing costs delay the benefit. The Refinance Calculator shows payment, break-even, and interest together for that reason.
Should closing costs be financed into the new loan?
Financing closing costs raises the new principal and interest. The Refinance Calculator should include financed costs in the new balance when that is how the loan will close. Cash-paid costs enter the break-even numerator instead.
How does this relate to mortgage and payoff tools?
The Mortgage Calculator sizes payments and full schedules. The Mortgage Payoff Calculator focuses on extra payments and time to clear a balance. The Refinance Calculator is the decision layer that compares two loans and break-even timing on QuickCalculators.
Summary
The Refinance Calculator subtracts the new payment from the old to find monthly savings, divides closing costs by that savings for break-even, and compares remaining interest minus new interest minus costs for lifetime savings. Saving $150 per month with $3,600 in closing costs breaks even in 24 months; leaving sooner forfeits the cost recovery on that measure.
A longer new term can cut the payment while raising total interest, so payment, break-even, and lifetime interest must be read together. Results depend on the assumptions entered and are estimates for information only, not lending advice.