Use this tool to run two loans through the same amortization math and set the results side by side. It reports each loan's payment, total interest and total cost, so the cheaper one is obvious.
By the Personalloaner Editorial Team · Last updated 2026-09-16
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Enter your numbers and press Calculate. Nothing you type leaves your browser.
How we get paid: if you apply through the link above, a lending partner may send us a referral fee. It never changes the rate you are offered or what we publish. We are not a lender and we do not process applications. The lowest rates are only available to the most qualified applicants. Full disclosure.
How this calculator works
Two loans of the same size can cost very different amounts. The tool runs the amortization equation on both and lays the results out together.
For each loan: M = P * r * (1 + r)^n / ((1 + r)^n - 1), and total interest = M * n - P.
P = amount borrowed, the same for both loans
r = monthly rate = annual rate / 12 / 100
n = number of monthly payments
The cheaper loan is the one with the lower total cost, and that is not always the one with the lower payment. Stretching the term can lower the payment while lifting total interest.
Use the rates from offers you actually hold. Rates move with the lender and your credit profile.
Common questions
Why look at total interest, not only the payment?
A small payment often reflects a long term, and that adds months of interest. Total interest captures what each loan really costs.
Can I compare loans of different terms?
You can, but look at both the payment and the total interest. A longer term tends to cut the payment and lift the total.
Are fees part of the comparison?
They are not. Principal and interest are all that get compared here. Use the APR calculator to see how upfront fees change each loan's yearly cost.
What does a tie tell me?
Both loans round to the same total interest. Use the monthly payment and any fees to choose between them.
