Interest Rate Calculator
Quick answer
Divide APR by 12 for monthly periodic rate on standard monthly loans unless your contract says otherwise.
For a related estimate, see Apr Calculator.
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Periodic rate
Monthly r = APR/12 for standard loans; daily r = APR/365 for many card accruals.
Explore further: Credit Card Calculator · Credit Card Interest Calculator
This intent is for users translating “6% per year” into monthly periodic rate or comparing simple interest buckets. Different from APR: fewer fee effects, more rate algebra.
How to use this calculator
- APY vs APR: Savings products quote APY; loans often APR—do not mix without conversion.
- Daily periodic rate: Credit cards often use daily rate × average daily balance.
- Tiered balances: Some products use stepped rates—use schedule if provided.
Real-world examples
- Example: 18% APR → ~1.5% monthly periodic; 6% APR → ~0.5% monthly (illustrative).
- Sensitivity check: Nudge the rate by about +0.5% and the principal by about −5%. If the payment, break-even, or target amount moves enough to change your decision, you are still on a steep part of the curve where small inputs matter.
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What this means
Periodic rate translation explains finance charges—cards and loans use different day-count conventions.
FAQ
Is this a loan commitment?
No. Outputs are educational estimates. Final payments, APR, and fees come from your lender’s disclosures.
How accurate is this calculator?
It applies standard math to the inputs you enter. Real lenders, payroll rules, and rounding can differ—use results for planning and comparison, not as binding quotes.
Why might my result differ from another website?
Different assumptions (APR vs note rate, day-count, tax year, rounding mode, or unit definitions) shift outputs slightly. Align inputs with the same definitions when you compare.