Interest Rate Calculator
Estimate the fixed monthly rate implied by a loan amount, term, and payment.
The result is an implied fixed rate, not an APR quote. Fees are not included.
Known loan details
Enter the contractual monthly payment, excluding taxes and insurance.
Estimated amortization
Repayment share
Monthly schedule
| Month | Payment | Interest | Principal | Balance |
|---|
Detailed Breakdown
Method
The calculator solves for monthly rate i so the
standard amortized payment formula matches the entered monthly
payment. It uses numerical search because the rate is not isolated
directly in the formula.
Interpretation
The displayed nominal annual rate is the solved monthly rate multiplied by 12. Total payments are monthly payment times term; interest is total payments minus principal.
Limits
The model assumes one fixed rate and equal monthly payments. Upfront fees, insurance, changing rates, and irregular payments are excluded, so the result can differ from APR.
No solution
If the payment is below principal divided by the number of months, it cannot repay the loan at a non-negative rate. Increase the payment or change the term/principal.
Examples
Enter a loan's principal, monthly payment, and remaining term to estimate the fixed rate implied by that schedule. The result changes when any of these values changes.
FAQ
Is the estimated rate the same as APR?
Not necessarily. This calculation estimates a rate consistent with entered payments; fees and local APR rules are not automatically included.
Why might there be no solution?
Some combinations of principal, payment, and term cannot be represented by the supported nonnegative fixed-rate model.
Are extra or irregular payments included?
No. Use the scheduled monthly payment and remaining term. Irregular extra payments require a separate model.
Related Calculators
- Payment Calculator — solve for a scheduled payment.
- APR Calculator — estimate a fee-inclusive borrowing rate.
- Loan Calculator — view payments and amortization.
Internal links: verify a payment using the Payment Calculator and compare fees with the APR Calculator.