Loan Calculator
It calculates the fixed monthly repayment, total repaid and total interest for any amortizing loan — personal, auto or student.
Monthly repayment
$566.40
Total interest
$5,984
Total repaid
$33,984
Interest / principal
21.4%
What it calculates
It calculates the fixed monthly repayment, total repaid and total interest for any amortizing loan — personal, auto or student.
Why it matters
The advertised rate is not the cost. Total interest depends just as much on term length as it does on APR.
Who it's for
Anyone comparing loan offers, refinancing existing debt, or checking whether a monthly repayment fits their budget.
Formula
- P
- Amount borrowed
- r
- Monthly interest rate
- n
- Number of monthly payments
Worked example
$20,000 auto loan at 7% over 5 years
- 1r = 7% ÷ 12 = 0.005833
- 2n = 60
- 3M = 20,000 · r(1+r)⁶⁰ / ((1+r)⁶⁰ − 1)
Monthly ≈ $396, total interest ≈ $3,761
How the loan calculator works
Every payment covers the interest accrued that month first; the remainder reduces the balance. Because the balance falls, the interest portion shrinks each month while the payment stays constant.
The same fixed-payment formula behind mortgages applies to car, personal and student loans: each payment covers the month's interest first, and whatever is left reduces the balance.
Shortening the term raises the monthly payment but cuts total interest sharply — compare 5 vs 7 years to see the difference.
Common mistakes
- Choosing the longest term to get the lowest monthly payment, and paying far more interest.
- Ignoring origination or application fees, which are not in the interest rate.
- Confusing APR with a flat rate quoted on the original balance.
Tips and best practice
- Run each term you are offered and compare total interest, not monthly cost.
- Check for early repayment penalties before planning to overpay.
Frequently asked questions
What is the difference between APR and interest rate?
The interest rate prices the borrowing itself; APR also folds in compulsory fees, so it is the better comparison figure.
Does a longer loan term cost more?
Almost always. Monthly payments fall, but you pay interest for more months on a slower-shrinking balance.
Can I use this for a student loan?
Yes, for fixed-rate, fixed-term student loans. Income-contingent government loans repay differently.
Does overpaying reduce my monthly payment?
Usually it shortens the term instead. Some lenders will recalculate the payment on request.
Related calculators
Further reading
Methodology & trust
- Formula source
- Standard amortizing loan formula.
- Last updated
- 2026-07-28
- Privacy
- Every calculation runs in your browser. No inputs are sent to a server or stored.
- Accessibility
- Keyboard navigable, labeled inputs and WCAG AA color contrast.