Result
How to use this calculator
Enter your loan amount and the rate you were quoted for each term. The calculator shows the monthly payment, total interest, and payment difference side by side — no need to run two tools and compare by hand.
The formula
Both sides use the standard amortization formula M = L × r(1+r)^n ÷ ((1+r)^n − 1). The 15-year side uses the 15-year rate and 180 payments; the 30-year side uses its rate and 360 payments.
Example: $400,000
At 5.5% for 15 years vs 6.5% for 30 years: the 15-year payment is about $3,267.86 vs $2,528.39 — but total interest is roughly $188,000 vs $510,000. The shorter term costs $739 more per month and saves about $322,000 in interest.