Free · Interest & savings
Interest Compounding & Effective Rate Calculator
Compare nominal interest with effective interest at different compounding frequencies.
- Formula & worked example
- Private in your browser
- No signup
Your calculation
Enter enough known values to calculate the blanks.
Use one currency for your figures. Mixed-currency conversions use rates captured October 5, 2026, rather than live exchange rates.
How to use this calculator
- Enter the values you know in the units shown. Leave unknown values blank.
- Results update automatically as you type. Edit a result to calculate another value, or lock a value to keep it fixed.
- Reset restores the starting fields. A worked example appears below.
Use the result with context
Results are estimates for planning and education. Confirm rates, taxes, fees, and legal requirements with the relevant institution or a qualified professional before making a financial decision.
Formula and method
An effective annual rate includes interest earned or charged on earlier interest. More frequent compounding raises the effective rate for a fixed positive nominal rate.
Effective annual rate = (1 + annual rate / frequency)^frequency − 1; continuous rate = exp(annual rate) − 1. Rates in these formulas are decimals.
Worked example
Enter these known values and leave the other values blank.
- Annual interest rate
- 12 %
- Compounding frequency
- Monthly
- Term
- 120 yrs / mos
- Initial balance
- 1000 USD
- Periodic rate
- 1 %
- Effective interest rate (EIR)
- 12.683 %
- Final balance
- 3300.39 USD
Assumptions and limitations
- Inputs must satisfy the validation rules. Editing a result can recalculate an earlier input; lock values you want to keep fixed.
- Currency conversions use the captured source rates from October 5, 2026; they are not live exchange rates.
Common questions
What does this effective annual rate calculation tell me?
An effective annual rate includes interest earned or charged on earlier interest. More frequent compounding raises the effective rate for a fixed positive nominal rate.
Can I calculate a different unknown?
Yes. Clear that field and enter the other known values. The calculator uses the available inverse equations.
References
The calculation equations, inverse formulas, units, and input rules were imported from this source. Bookify provides the interface and equation solver.
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