Find out exactly how much interest you'll pay over the life of a loan, and see how rate and term change the total.
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Interest as % of Principal
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How the Loan Interest Calculator works
Every payment on an amortized loan is split between interest and principal. This tool runs the
full amortization schedule for your loan and adds up every month's interest charge to show you
the total interest you'll pay over the entire term — not just the interest rate, but the actual
dollar amount.
It also shows that total as a share of your original principal, which makes it easy to compare
how expensive different rate-and-term combinations really are, even when the monthly payment
looks similar.
Total Interest = Total of all payments − Principal
Two loans with the same interest rate can have very different total interest costs depending on
the term — a longer term spreads out a smaller payment but keeps you paying interest for more
months, which usually raises the total.
Frequently asked questions
Total interest is the sum of the interest portion of every monthly payment over the life of the loan — found by running the full amortization schedule and adding up the interest charged each month, which is Total Interest = Total of all payments − Principal.
Usually, yes, if the term stays the same — a lower rate means less interest is charged on your balance each month. But if a lower rate comes with a longer term, you could still end up paying more total interest, since interest keeps accruing for more months.
Generally, yes. A longer term lowers your monthly payment, but your balance stays higher for longer, so more total interest accrues over the life of the loan — even at the same interest rate.
The most effective ways are borrowing less, choosing a shorter term, securing a lower rate, or making extra payments toward principal. Try the Extra Payment Loan Calculator to see how much a single extra payment could save you.