Understand this tool
Plan a loan with the full cost in view
- What the concept means
- An amortizing loan is repaid through scheduled payments that cover periodic interest and progressively reduce principal.
- Why it exists
- The calculator turns principal, APR, and term into an estimated fixed payment and total interest.
- When to use it
- Use it to compare otherwise similar fixed-rate installment-loan scenarios before reviewing an actual disclosure.
- What the result means—and does not mean
- The payment is a mathematical principal-and-interest estimate. It is not approval, a quote, or a complete cost including origination fees, insurance, late charges, or variable-rate changes.
How amortization moves through time
Interest for each period is calculated from the remaining balance. Early payments generally contain more interest because the balance is larger; later payments direct more money to principal.
A longer term can lower the required monthly payment while increasing the number of interest-bearing periods. That is why the smallest payment is not automatically the lowest-cost loan.
Key concepts
Key concepts
- Loan principal
- The amount financed before interest.
- APR
- An annualized borrowing-rate disclosure; its exact legal composition depends on jurisdiction.
- Amortization
- Repaying a balance through scheduled principal and interest payments.
- Fixed payment
- A payment amount that remains constant in this model.
- Loan term
- The number of months or years allowed for repayment.
- Total interest
- All modeled payments minus original principal.
Method or process
Calculation method
How amortization moves through time
Interest for each period is calculated from the remaining balance. Early payments generally contain more interest because the balance is larger; later payments direct more money to principal.
A longer term can lower the required monthly payment while increasing the number of interest-bearing periods. That is why the smallest payment is not automatically the lowest-cost loan.
Formula or rule
payment = P × [i(1 + i)^n] / [(1 + i)^n − 1]Compare the concepts
Payment size and total cost
| Choice | Monthly payment | Typical total interest |
|---|---|---|
| Shorter term | Higher | Lower |
| Longer term | Lower | Higher |
Common mistakes
Common mistakes
- Choosing by monthly payment alone.
- Treating APR and note rate as universally identical.
- Leaving fees and optional products out of a real comparison.
Edge cases and limits
Edge cases and limits
- At 0% APR, principal is divided evenly across payments.
- Extra or irregular payments require a fuller amortization schedule.