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Nominal vs effective rate; quarterly rate from monthly

Short answer

Nominal rate ignores compounding within a period; effective rate includes it. With 1% monthly, effective quarterly rate = (1.01)^3 - 1 = 3.0301% (nominal quarterly 3%).

Differentiate between nominal interest rate and effective interest rate. If monthly interest rate is 1%, what will be the quarterly interest rate?

Nominal vs effective interest rate

PointNominal rateEffective rate
DefinitionStated rate for a year (or period), not counting compounding inside itActual rate for the period after compounding
Calculationr = rate per sub-period × mi = (1 + r/m)^m − 1
CompoundingIgnoredIncluded
ValueLower (or equal)Higher (or equal)
Example12% per year, compounded monthly12.68% per year
Use in formulasNot used directlyUsed in factors once period matches payment period

Quarterly rate from monthly rate

Monthly rate = 1%, and a quarter has 3 months.

  • Nominal quarterly rate = 3 × 1% = 3%
  • Effective quarterly rate i = (1 + 0.01)^3 − 1 = 1.030301 − 1 = 3.0301%

Answer: the quarterly interest rate is 3.03% (effective); the nominal quarterly rate is 3%.

✓ Answer checked by Claude Opus 5.5 (high effort)

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