Mortgage Interest Rate Change Calculator
Compare how different interest rates affect your monthly payments and long-term costs.
How a Rate Change Affects Your Wallet
Interest rates are the most significant factor in determining the long-term affordability of your home. Even a small fraction of a percentage point—often referred to as a "basis point"—can translate into tens of thousands of dollars over a 15- or 30-year period.
When interest rates drop, homeowners often consider refinancing to lower their monthly overhead. Conversely, when rates rise, the purchasing power of new buyers decreases, as they can afford less house for the same monthly payment.
The Math Behind the Calculation
To calculate a mortgage payment (Principal and Interest), we use the standard amortization formula:
M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
- M: Total monthly payment
- P: Principal loan amount
- i: Monthly interest rate (Annual rate / 12)
- n: Number of months (Years × 12)
Real-World Example
Imagine you have a $400,000 mortgage on a 30-year fixed term:
- At a 7% interest rate: Your monthly payment is approximately $2,661.
- At a 6% interest rate: Your monthly payment drops to $2,398.
- The Result: Saving 1% in interest puts $263 back in your pocket every single month. Over 30 years, that is a staggering $94,680 in interest savings.
Frequently Asked Questions
Is it worth refinancing for a 0.5% rate drop?
Generally, experts suggest looking at a refinance if you can drop your rate by 0.75% to 1%. However, if you plan to stay in the home for a long time, even a 0.5% drop can cover the closing costs of the refinance within a few years and lead to long-term savings.
Does this include property taxes and insurance?
No, this calculator focuses strictly on Principal and Interest (P&I). Your total monthly housing payment will also include escrow items like property taxes, homeowners insurance, and potentially Private Mortgage Insurance (PMI).