Mortgage Savings Calculator
Monthly Savings vs. Total Interest Savings
Refinancing produces two distinct types of savings that don't always move in the same direction:
- Monthly savings — the immediate cash flow improvement: how much less you pay each month after refinancing.
- Total interest savings — the reduction in cumulative interest paid over the full lives of both loans.
These can diverge significantly when you change your loan term. Refinancing from 20 years remaining into a new 30-year term lowers your monthly payment but restarts a longer amortization clock — you may pay less each month but more in total interest, even at a lower rate.
When Both Move in the Same Direction
The ideal refinance cuts both monthly payment and total interest. This happens when you get a significantly lower rate and keep a similar term, or shorten the term enough that faster principal paydown outweighs a higher monthly payment.
When They Diverge
Extending your term while lowering your rate reduces monthly payments but may increase total interest. The calculator flags this — you'll see a positive monthly savings alongside a negative interest difference. Use the 5-year and 10-year net savings rows to gauge how long you'd need to stay for the monthly savings to outweigh the total interest penalty.
The Savings Formula
Here's the exact math behind each result in the calculator:
P&I uses the standard amortization formula: Balance × [r(1+r)ⁿ] / [(1+r)ⁿ − 1], where r = monthly rate and n = term in months.
The 5-year and 10-year rows use (Monthly Savings × months) − Closing Costs — a cash-flow snapshot of where you stand at that point in time, regardless of when either loan ends.
How Loan Term Affects Total Savings
The choice of new term has a dramatic effect on total savings. Here's a comparison for a $320,000 balance refinancing from 7.25% with 28 years remaining:
| New Term | New Rate | New Payment | Monthly Δ | Total Interest | Interest Saved |
|---|---|---|---|---|---|
| 30 yrs | 6.50% | ~$2,023/mo | −$203/mo | ~$408K | ~$19K |
| 25 yrs | 6.50% | ~$2,162/mo | −$64/mo | ~$329K | ~$98K |
| 20 yrs | 6.50% | ~$2,393/mo | +$167/mo | ~$254K | ~$173K |
| 15 yrs | 6.25% | ~$2,747/mo | +$521/mo | ~$174K | ~$253K |
The 15-year loan saves $253K in total interest — but costs an extra $521/mo. The 30-year refinance saves only $19K total but reduces monthly cash needs by $203. The right choice depends on your cash flow, how long you'll stay, and your financial goals.
Net Savings After Closing Costs
The break-even point is where cumulative monthly savings cover your upfront closing costs. Until that month, you are net-negative on the refinance.
Example: $6,000 closing costs at $200/month savings → break-even in 30 months. After 5 years: ($200 × 60) − $6,000 = $6,000 net. After 10 years: ($200 × 120) − $6,000 = $18,000 net.
No-Closing-Cost Refinances
Some lenders roll fees into the loan balance or accept a slightly higher rate in exchange for zero upfront costs. Set closing costs to $0 in the calculator — break-even is immediate, but your monthly savings will be smaller since the higher rate or balance offsets the fee waiver.
How Long Will You Stay?
The break-even is the floor. Most financial advisors target a break-even under 36 months as a baseline for a worthwhile refinance. If you plan to stay 5–10 years past break-even, the monthly savings compound into substantial lifetime gains.
Frequently Asked Questions
How do I calculate my refinance savings?
Monthly savings = current monthly payment minus new monthly payment. Total interest savings = total interest on the current loan minus total interest on the new loan. Net savings = total interest savings minus closing costs. Break-even = closing costs divided by monthly savings.
Does a lower rate always mean total savings?
Not if you extend your term. Refinancing from 20 years remaining into a 30-year loan at a lower rate lowers monthly payments but adds a decade of additional payments. At some rate spreads, the extra years of interest outweigh the rate reduction. The total interest rows in the calculator tell you exactly which way your specific scenario goes.
What closing costs should I expect?
Typical refinance closing costs run 2–5% of the loan balance. Common fees include origination (0.5–1%), appraisal ($400–$700), title insurance ($500–$1,500), and recording fees ($50–$200). On a $320,000 balance, expect $6,400–$16,000. Use your lender's Loan Estimate for an accurate break-even calculation.
How long do I need to stay to benefit?
At minimum, through the break-even point. If closing costs are $6,000 and monthly savings are $200, break-even is 30 months. If you sell or refinance again before then, you'll have paid closing costs without recovering them. Most advisors recommend targeting a break-even under 36 months.
Related Guides
- Refinance Break-Even Calculator — How Many Months to Recoup Closing Costs?
- PMI Removal Calculator — When Does Your PMI Drop Off?
- How Much Can You Save by Refinancing? Real Examples
- Mortgage Refinance Closing Costs: Every Fee Explained
- How to Compare Refinance Offers Side by Side
- The 1% Refinance Rule of Thumb
- Full Refinance Calculator — Compare Multiple Lender Offers
Ready to Compare Lender Offers?
The full RefinanceUSA calculator lets you enter multiple lender offers side by side and shows your exact payment, savings, and break-even for each — so you can pick the offer that actually saves you the most.
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