Interest Calculator
Quick answer
Enter balance, APR, and term—or payment and derive interest from schedule. Focus on cumulative interest in the first 5 years on long loans.
For a related estimate, see Apr Calculator.
Explore further: Auto Loan Calculator · Car Loan Calculator
What moves the payment
Fixed-rate amortizing loans use principal, APR, and term. APR calculators include fees in the effective rate. Credit cards revolve—interest compounds on average daily balance. Debt payoff order changes total interest when you redirect surplus dollars.
Explore further: Credit Card Calculator · Credit Card Interest Calculator
This intent is “how much interest will I pay,” not just payment. It helps users see early-year interest on amortizing loans and compare total interest across terms when payment is held constant or not.
How to use this calculator
- Front-loaded interest: Amortizing loans charge more interest when balance is high.
- Extra principal: Even small adds early can reduce lifetime interest materially.
- Simple vs compound: Most consumer installment loans use monthly compounding conventions—verify for your product.
Real-world examples
- Example: $200k @ 6.5% / 30 years: First-year interest can exceed $12k even as principal barely moves (illustrative).
- Sensitivity check: Nudge the rate by about +0.5% and the principal by about −5%. If the payment, break-even, or target amount moves enough to change your decision, you are still on a steep part of the curve where small inputs matter.
Explore further: Credit Card Payoff Calculator
What this means
Cumulative interest is the product of rate, balance path, and time—reducing any of the three reduces cost.
FAQ
Is this a loan commitment?
No. Outputs are educational estimates. Final payments, APR, and fees come from your lender’s disclosures.
How accurate is this calculator?
It applies standard math to the inputs you enter. Real lenders, payroll rules, and rounding can differ—use results for planning and comparison, not as binding quotes.
Why might my result differ from another website?
Different assumptions (APR vs note rate, day-count, tax year, rounding mode, or unit definitions) shift outputs slightly. Align inputs with the same definitions when you compare.