Rate Comparison Calculator
Compare two interest rates side-by-side. See how even a small rate difference adds up over 30 years.
Rate A: 6.5%
$2,022.62
/month
Rate B: 5.75%
$1,867.43
/month
💡 Plain English: A 0.75% rate difference on a $320,000 loan over 30 years means $155.18/mo difference in your payment — and $55,866 in total interest over the life of the loan. That's why shopping around for the best rate matters so much: even 0.25% can save you thousands.
About the Rate Comparison Calculator
Even a small difference in interest rate changes your monthly payment and the total interest you pay over the life of the loan. This calculator places two rates side by side so you can see exactly what a rate difference costs — or saves.
How this calculator works
Enter the loan amount, term, and two interest rates to compare. The calculator shows the monthly payment and total interest for each, plus the difference between them.
The math, in plain English
For each rate, the monthly payment is computed with the amortization formula M = P × [r(1+r)^n] / [(1+r)^n − 1]. Total interest = (monthly payment × n) − loan amount.
Key terms
- •Interest rate — the annual cost of borrowing
- •Monthly payment — what you pay each month under each rate
- •Total interest — the lifetime interest cost of each loan option
Tips & things to know
- ✓A 0.5% rate difference on a $300,000 loan can mean tens of thousands of dollars over 30 years.
- ✓Compare the total interest, not just the monthly payment, when choosing between rates.
- ✓Paying "points" upfront can lower your rate — weigh the upfront cost against long-term savings.
Frequently asked questions
Is a lower rate always better?+
Usually yes, but if you pay discount points or fees to get the lower rate, calculate how long it takes to recoup that cost.
How much does 1% off my rate save?+
On a 30-year loan, a 1% lower rate can reduce your monthly payment significantly and save tens of thousands in interest.
This calculator is for educational purposes only and uses estimates. Always consult a licensed mortgage professional for advice specific to your situation.