Know the Real Cost Before You Sign
You’re buying a house and the listing price is $250,000. The bank offers 6.5% over 30 years. Your monthly payment? About $1,580. But here’s the number that really stings: you’ll pay roughly $319,000 in interest over the life of that loan. That’s more than the house itself.
Most people focus on whether they can afford the monthly payment. But the total interest cost, that’s the number that should keep you up at night. Or at least make you consider a 15-year term instead.
What You Get
Enter three things: loan amount, annual interest rate, and term in years. The calculator instantly shows your monthly payment, total amount paid, and total interest cost. Click to expand the full amortization schedule and you’ll see a month-by-month table showing exactly how each payment splits between principal and interest.
That amortization schedule is revealing. In the early years of a 30-year mortgage, most of your payment goes to interest, you’re barely touching the principal. It takes years before the split starts to favor actually paying off the house. Seeing this in a table makes it visceral in a way that just knowing the monthly payment doesn’t.
The Comparisons That Matter
Mortgage shopping. Same $300,000 house, but one lender offers 6.25% and another offers 6.75%. Over 30 years, that half-percent difference costs you tens of thousands in interest. Run both scenarios.
Term length. A $25,000 car loan at 5.9%, should you go for 48 months or 72 months? The monthly payment drops significantly with the longer term, but you’ll pay thousands more in total interest. This calculator makes that tradeoff concrete.
Refinancing. You’re three years into a 6.8% mortgage and rates have dropped to 5.5%. Is it worth the closing costs to refinance? Calculate the remaining balance scenario and compare.
Student loans. Before signing that promissory note, run the numbers on your expected starting salary versus the monthly payment. Can you actually afford this?
The Compound Interest Calculator shows the flip side, what happens when compounding works in your favor through savings and investments. The Percentage Calculator helps with quick rate comparisons.
Technical Notes
The formula is the standard amortization equation: Monthly Payment = P x r x (1+r)^n / ((1+r)^n - 1), where P is the principal, r is the monthly rate (annual rate / 12), and n is total payments. This handles fixed-rate loans only, adjustable-rate mortgages need a different approach. Your financial data stays in your browser.