Loan Calculator
Calculate monthly payments and total interest for a fixed-rate loan. Compare extra principal payments and inspect the repayment schedule.
Monthly principal + interest
Fixed interest with monthly amortization. Uses the entered interest rate; APR fees, variable rates and prepayment penalties are not modelled. Optional extra payments are applied to principal after monthly interest.
Your repayment plan
Fixed interest rate, monthly payments and no lender rounding or changing fees. Taxes and insurance stay outside this loan balance.
| Year | Payments | Principal | Interest | Balance |
|---|---|---|---|---|
| 1 | $3,650.63 | $3,135.94 | $514.69 | $6,864.06 |
| 2 | $3,650.63 | $3,329.36 | $321.28 | $3,534.70 |
| 3 | $3,650.63 | $3,534.70 | $115.93 | $0.00 |
Formula checked · NumberSwift · Review process
For informational purposes only. Results are estimates and do not constitute financial advice.
How this calculator works
A fixed-rate loan has a scheduled monthly payment. Each month, interest is charged on the remaining balance before the payment reduces principal. Optional extra principal reduces the balance faster, saving interest. The final payment is capped at the amount owed. Lender rounding, APR fees and prepayment charges can change the actual schedule.
Formula
Monthly payment = P × r / (1 − (1+r)^(−n)), where P is financed principal, r = annual interest rate (%) / 100 / 12 and n = years × 12. At 0% interest, payment = P/n. Interest each month = outstanding balance × r.
Assumptions & limitations
Fixed interest with monthly amortization. Uses the entered interest rate; APR fees, variable rates and prepayment penalties are not modelled. Optional extra payments are applied to principal after monthly interest.
Sources & reference material
- OpenStax: annuities ↗
Background for fixed periodic payments and contributions.
Worked example
A $10,000 loan at 6% over 3 years has 36 scheduled monthly payments of about $304.22. The monthly rate is 0.06 ÷ 12 = 0.005. Total interest is about $951.90 and total repayment is $10,951.90 before fees. The model uses unrounded payments internally, so multiplying the displayed payment can differ by a few cents.
If your monthly payment is already fixed and you need the payoff time instead, use the Debt Payoff Calculator.
Our approach to calculations ↗Common questions
Is the entered rate the same as APR?
Not necessarily. This model applies the entered interest rate monthly. APR can include fees and use different disclosure conventions.
Does a longer term cost more?
At the same positive rate and principal it generally lowers the scheduled payment but increases total interest. Compare both outputs.
Can I model a variable-rate loan?
No. This model keeps the rate fixed for the whole term; variable rates and balloon payments require a different schedule.