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Finance

Mortgage Refinance Break-Even Calculator

When market rates fall — or your mortgage exits its lock-in period — the obvious question is whether refinancing is worth it. This tool compares the monthly payment on your current loan vs. a new one, shows how many months of savings it takes to recoup the closing costs (legal fees, penalties, valuation, application charges), and then tells you whether the whole loan saves or costs more over its full life.

Break-even = closing costs ÷ monthly savings. Assumes the new principal equals the current remaining balance (cash-out and lender rebates are not modelled).

Current mortgage

New loan (after refinance)

Monthly savings

Current monthly payment:

Break-even point

Total lifetime savings

= (remaining payments on current loan) − (total payments on new loan + closing costs). A negative figure means refinancing costs more overall.

Remaining interest (current)

Total interest (new)

Formula

Monthly rate i = annual rate / 12 / 100 Monthly payment P = L × i × (1 + i)ⁿ / ((1 + i)ⁿ − 1) Monthly savings = P_old − P_new Break-even months = closing costs ÷ monthly savings Lifetime savings = P_old × remaining months − (P_new × new term + closing costs)

Frequently asked

How quick a break-even is "worth it"?

A common rule of thumb: refinancing is worth it if you intend to stay in the home (or hold the loan) for longer than the break-even period. Most people aim for 24–36 months. If the break-even period stretches beyond 5 years, or you may sell within 3 years, the savings probably won't materialise. Also watch the "Total lifetime savings" tile — even with lower payments, stretching a 15-year mortgage into a fresh 30-year loan can flip the lifetime total into negative.

Why is my monthly payment lower but my lifetime savings negative?

You're stretching the schedule. Example: 15 years left at 5 % → refinance to a fresh 30 years at 4.5 %. The monthly payment drops sharply, but you're paying interest over 360 months instead of 180 — adding 15 years of new interest charges. The longer schedule can outweigh the lower rate. If you want pure rate savings, keep the new term equal to the remaining months: the monthly drop will be smaller but lifetime savings stays positive.

How should I handle the lender's cash rebate?

Subtract the rebate from closing costs and use the net figure. Example: legal + valuation + prepayment penalty = $25,000, lender rebate = $15,000, so net closing cost = $10,000. Watch the rebate claw-back: many rebates are repayable if you sell or refinance again within 2–3 years; if you might exit early, treat the rebate as zero and use the gross closing costs instead.

Does this work for variable-rate / adjustable-rate mortgages?

Yes for a rough cut — enter today's effective rate. The model assumes the rate is fixed for the full term, so if benchmark rates swing, real-world payments will drift. Best practice: also run a "stressed-rate" scenario (current rate + 1–2 percentage points) to see whether the break-even period still looks acceptable. Going from variable-rate to a new fixed-rate loan needs explicit assumptions about future rate paths — this tool can only show the deal at today's rate.

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