Finance · Savings & Banking

Effective Interest Rate Calculator

Convert a nominal annual rate to an effective annual rate.

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Quick guide

How to use this calculator

  1. Enter the balance, rate, timing, fee, or contribution assumptions named by the fields.
  2. Use one currency and follow the stated nominal, effective, simple-interest, or compounding convention.
  3. Review the calculator-specific assumptions before comparing accounts or making a savings decision.

Calculation method

Calculation method

Effective annual rate = (1 + nominal rate ÷ m)^m − 1.

Entered fixed decimals are parsed exactly. Compound projections use stable exponential forms and preserve zero-rate cases exactly; money rounds only for display and a supported nonzero amount is not replaced by a misleading zero.

Worked example

Worked example

A 12% nominal annual rate compounded monthly has an effective annual rate of about 12.6825%.

Effective annual rate = (1 + nominal rate ÷ m)^m − 1.

Supported inputs

Precision and limits

Visible input limits

Amounts accept up to 30 digits and 12 decimal places and are capped at 1e12 per input. Rates are capped at 1000%. Most projections are capped at 1,200 months or 100 years; narrower whole-number limits appear in field labels.

International scope

No currency, institution, current market rate, deposit-insurance rule, tax system, regulatory disclosure, or jurisdiction-specific product term is assumed.

Decision boundary

Results are arithmetic scenarios from visitor-entered assumptions, not account quotations, forecasts, tax advice, legal determinations, deposit guarantees, or recommendations.

Calculator-specific assumptions

This conversion excludes fees and cash-flow timing beyond compounding. It is not a borrowing APR disclosure.