APR Calculator
Back into the interest rate that makes an amortizing loan’s payment pencil out — enter principal, payment, and term. Click any i for detail.
Loan & payment
Loan amount ($)
i
Loan amount
Principal being financed (amount you owe at start). |
|
|---|---|
Payment amount ($/mo)
i
Payment
Fixed monthly principal & interest payment. |
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Term value
i
Term
Length of the loan in months or years (use the unit selector). |
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Term unit
i
Unit
Choose years or months for the term value above. |
How to use this calculator
- Enter the loan principal.
- Enter the fixed monthly P&I payment.
- Set term in years or months.
- Read the implied APR and interest totals.
Results explained
Headline APR is the annual rate that makes standard amortizing PMT match your payment. It is not a Truth-in-Lending APR that folds in fees.
Quick reference: APR solve
Solver uses the amortizing identity.
| Item | Detail |
|---|---|
| Identity | PMT(P, APR, n) = payment |
| Method | Bisection + Newton polish |
| 0% check | Payment must be at least principal ÷ months |
For payment from rate, use a mortgage payment tool instead.
How the estimate is built
Find APR such that Calcscape.loan.pmt(loan, APR, months) equals your payment.
Example scenario
$250,000 loan, $1,580/mo, 30 years → roughly mid-6% APR depending on exact payment.
FAQ
Is this the lender APR on my Loan Estimate?
Not necessarily — this ignores points and finance charges baked into official APR disclosures.
What if payment is too low?
If payment cannot amortize the loan even at 0%, the solver shows an error.
Months vs years?
Use the unit selector; 30 years = 360 months.