ToolPilot
Loan calculator
Fixed-rate installment loan: enter principal, annual interest, and term in years or months. See your monthly payment, total interest, amortization by year, and how much of what you pay is principal versus interest.
Loan details
$25,000
60 monthly payments
Results
Formula: M = P × r × (1 + r)n / ((1 + r)n − 1) with monthly rate r and n payments.
- Monthly payment
- $500.95
- Total interest
- $5,057
- Total payment
- $30,057
Principal vs interest
Share of total amount paid over the full term (principal borrowed vs interest charged)
Amortization summary
Principal and interest allocated per year (partial final year if the term is not a multiple of 12 months).
| Year | Principal paid | Interest paid | End balance |
|---|---|---|---|
| 1 | $4,282 | $1,730 | $20,718 |
| 2 | $4,614 | $1,397 | $16,104 |
| 3 | $4,972 | $1,039 | $11,132 |
| 4 | $5,358 | $653 | $5,774 |
| 5 | $5,774 | $237 | $0 |
How it works
For a fixed rate and equal monthly payments, the installment M = P × r × (1 + r)n / ((1 + r)n − 1) where P is the loan principal, r is the monthly interest rate (annual percentage divided by 12), and n is the number of months. Early payments are mostly interest; later ones pay down more principal. The yearly table sums the principal and interest portions of each payment within that year and shows the remaining balance after the last payment of the year. Display amounts use USD formatting for readability; the math is currency-agnostic.
FAQ
What if my interest rate is 0%?
The tool splits the principal evenly across all payments: monthly payment = loan amount ÷ number of months. Total interest is zero.
Does this include fees or insurance?
No. Origination fees, escrow, credit insurance, and other add-ons are not modeled. Add those separately if your lender bundles them into the payment.
Why might tiny rounding differences appear?
Floating-point arithmetic and rounding to cents can leave a few cents of drift on the final balance in some edge cases. Lenders apply their own rounding rules on disclosures.
Can I use this for variable-rate loans?
This calculator assumes a fixed rate for the entire term. Variable or stepped rates need a schedule that changes when the rate resets.