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Loans & Debt

How To Calculate Refinance Savings

Refinancing replaces one loan with another, usually at a lower rate. The monthly saving is the obvious gain, but closing costs and a possibly longer term mean the break-even point and the lifetime interest matter just as much.

Quick Answer

Saving = old payment - new payment; Break-even = costs / monthly saving

balance
Outstanding principal being refinanced
oldRate
Current interest rate
newRate
Rate on the new loan
costs
Closing costs paid at refinancing
breakEven
Months for savings to cover the costs

Compute the payment on the current loan and on the new one using the annuity formula, subtract for the monthly saving, then divide the closing costs by that saving to get the number of months to break even. A 300,000 balance cut from 6% to 4.5% over 30 years saves about 271 a month, recovering 5,000 of costs in roughly 19 months.

What Is Refinance Savings?

Refinancing means paying off an existing loan with the proceeds of a new one, usually to obtain a lower interest rate, a different term, or to release equity. The decision hinges on whether the savings justify the cost and the effort.

The monthly saving is found by computing the payment on the current balance at the old rate and at the new rate, then subtracting. Both payments come from the same annuity formula used for any amortising loan, so a lower rate always lowers the payment for the same remaining term.

Closing costs are the price of refinancing. They include origination fees, appraisal, title work and recording, and typically total 2% to 5% of the loan. Some lenders offer a no-cost refinance in exchange for a higher rate, which is simply a different trade-off between upfront cost and long-term interest.

The break-even point is the months of monthly saving needed to recover the closing costs. Divide the costs by the monthly saving. A shorter break-even is safer, because it means you recoup the outlay sooner and are less exposed if you move or refinance again.

If you plan to stay in the home for less than the break-even period, refinancing usually loses money. The break-even calculation is the single most important test, and it depends on how long you expect to keep the loan.

Extending the term lowers the payment further but can raise lifetime interest even at a lower rate. Resetting a 25-year remaining term to 30 years cuts the monthly figure but adds five years of payments, which may cost more in total than leaving the loan alone.

A rate reduction of about 1% or more is the traditional threshold at which refinancing becomes worth considering, though the exact figure depends on the balance, the costs and how long you stay. Smaller reductions can still work on a large balance if costs are low.

Cash-out refinancing borrows more than the outstanding balance and hands the difference to the borrower, which can consolidate higher-rate debt or fund a project. It resets the loan and raises the payment, and it converts unsecured debt into debt secured on the home, which increases the risk.

Shortening the term raises the monthly payment but slashes lifetime interest. Refinancing from a 30-year to a 15-year loan often achieves both a lower rate and a large interest saving, at the cost of a higher required payment each month.

The break-even should be recalculated with the costs rolled into the loan, which is common. If the costs are financed rather than paid upfront, the new balance is higher, so the saving is smaller and the break-even a little longer.

Tax treatment of mortgage interest varies by jurisdiction and has narrowed in many places. A refinance does not change the fundamental deductibility of interest, but the amount deductible tracks the new loan and its balance, so the after-tax saving may differ from the gross figure.

Refinancing is not free of risk. It resets the amortisation clock, so a borrower who refinances repeatedly may pay mostly interest for years without making real progress on the principal. Sometimes the better answer is to keep the existing loan and pay extra toward the principal.

Formula

Pmt = balance x r x (1+r)^n / ((1+r)^n - 1)

The annuity formula gives the payment for a given balance, rate and term.

SymbolMeaning
BBalance
rMonthly rate
nMonths

Break-even = costs / monthly saving

How long the monthly saving takes to recover the closing costs.

SymbolMeaning
CClosing costs
SMonthly saving

How To Calculate Refinance Savings

  1. 1

    Find the current payment

    Use the outstanding balance, the current rate and the months remaining on the existing loan.

  2. 2

    Find the new payment

    Use the same balance at the new rate over the new term. Both use the same annuity formula.

  3. 3

    Subtract for the monthly saving

    Old payment minus new payment is the amount saved each month before any change in tax treatment.

  4. 4

    Add up the closing costs

    Include origination, appraisal, title and recording fees. Total them, whether you pay them upfront or roll them into the loan.

  5. 5

    Divide for the break-even

    Closing costs divided by the monthly saving gives the number of months to break even. If that is longer than you plan to stay, refinancing likely loses money.

Examples

Example 1: 300,000 cut from 6% to 4.5% over 30 years

Balance
300,000
Current rate
6%
New rate
4.5%
New term
30 years
Closing costs
5,000
StepCalculationResult
Old payment300000 x 0.005 x 1.005^360 / (1.005^360 - 1)1,798.65
New payment300000 x 0.00375 x 1.00375^360 / (1.00375^360 - 1)1,520.06
Monthly saving1798.65 - 1520.06278.59

Result: The payment falls by about 278.59 a month, so the 5,000 of closing costs are recovered in roughly 18 months.

Example 2: A small rate cut with high costs

Balance
300,000
Current rate
6%
New rate
5.5%
New term
30 years
Closing costs
6,000
StepCalculationResult
Old payment300000 x 0.005 x 1.005^360 / (1.005^360 - 1)1,798.65
New payment300000 x 0.0045833 x 1.0045833^360 / (1.0045833^360 - 1)1,703.37
Monthly saving1798.65 - 1703.3795.28

Result: A half-point cut saves only about 95.28 a month, so the 6,000 of costs take over 60 months to recover.

Calculator

Monthly saving

$278.60

Current payment
$1,798.65
New payment
$1,520.06
Break-even in months
17.9472
Saving over the new term
$95,294.43

Values update as you type. This calculator covers the single scenario its formula assumes — see Common Mistakes for what it leaves out.

Prefer a full-width tool? Open the Refinance Savings calculator page.

Common Mistakes

  • Ignoring the break-even period

    If you move or refinance again before the costs are recovered, refinancing loses money. Always compare the break-even with how long you expect to stay.

  • Stretching the term without noticing

    Resetting to a new 30-year term lowers the payment but can raise lifetime interest even at a lower rate. Compare total interest, not only the monthly figure.

  • Rolling costs into the loan without recalculating

    Financing the closing costs raises the balance, which lowers the saving and lengthens the break-even. Recompute with the higher balance.

  • Chasing a small rate cut

    A reduction of less than about half a point rarely justifies the cost unless the balance is very large. Small cuts on modest balances often fail the break-even test.

  • Overlooking the cash-out risk

    A cash-out refinance turns unsecured debt into debt secured on the home. If circumstances change, the home is at risk where the original debt was not.

  • Resetting the amortisation clock repeatedly

    Each refinance restarts the schedule, so more of each payment goes to interest again. Serial refinancing can leave you barely closer to owning the home.

  • Forgetting the tax and insurance handling

    A refinance can change escrow arrangements and the deductibility of interest. Confirm how tax and insurance will be handled before signing.

FAQ

How much rate reduction makes refinancing worthwhile?

A reduction of about 1% is the traditional rule of thumb, though the real test is the break-even. A smaller cut can still work on a large balance with low costs.

What is the break-even point on a refinance?

The number of months of monthly saving needed to recover the closing costs. Divide the costs by the monthly saving. If it exceeds how long you plan to stay, refinancing is likely to cost you money.

Should I pay closing costs upfront or roll them in?

Paying upfront keeps the balance lower and shortens the break-even, but uses cash now. Rolling them in preserves cash at the cost of a slightly higher payment and a longer break-even.

Will refinancing lower my total interest?

Not automatically. A lower rate usually helps, but extending the term can offset it and even raise lifetime interest. Compare the total interest of both loans over the period you will hold them.

What is a cash-out refinance?

A refinance that borrows more than the outstanding balance and pays the difference to the borrower. It can consolidate other debt but converts it into debt secured on the home, which raises the risk.

Can I refinance to a shorter term?

Yes, and it often makes sense. A shorter term usually comes with a lower rate and much lower lifetime interest, though the required monthly payment is higher.

References

  1. [1]Consumer Financial Protection Bureau, Refinancing a mortgage — https://www.consumerfinance.gov/owning-a-home/
  2. [2]Federal Reserve, Mortgage refinance — https://www.federalreserve.gov/consumerscommunities/community-development.htm
  3. [3]Investopedia, Refinance — https://www.investopedia.com/terms/r/refinance.asp