How to use the EFFECT() function in Excel

Calculates the effective annual interest rate (compounded) from a nominal annual rate, accounting for intra-year compounding periods.

Syntax

EFFECT(Nominal_Interest; Periods)

Arguments

• Nominal_Interest (required)
  The stated annual nominal interest rate (e.g., 0.05 for 5%). Must be > 0.
• Periods (required)
  The number of compounding periods per year (e.g., 12 for monthly). Must be ≥ 1 (decimal places truncated).

Error Handling

• #VALUE! if non-numeric inputs are provided.
• #NUMBER! if:
  • Nominal_Interest ≤ 0.
  • Periods < 1.

Background

• Nominal vs. Effective Rates:
  • Nominal rates ignore compounding (e.g., 5% annual, paid monthly = 5%/12 per period).
  • Effective rates reflect actual annual yield after compounding (e.g., 5% nominal → ~5.12% effective for monthly compounding).
• Formula:

Examples

1. Savings Account
   • Scenario: $1,000 deposited at 5% nominal interest, compounded monthly.
   • Calculation:

=EFFECT(5%, 12)  → Returns **5.12%**

1. • Verification:
     • Monthly interest: 5%/12 = 0.4167%.
     • Year-end balance: =FV(5%/12, 12, , -1000) = $1,051.16.
     • Effective yield: (1051.16 / 1000) – 1 = 5.12%.

1. Mortgage Loan
   • Scenario: Bank offers 2.42% nominal rate, compounded monthly.
   • Calculation:

=EFFECT(2.42%, 12)  → Returns **2.45%** (matches advertised effective rate). 

1. • Note: Banks may use alternative methods; exact matches may be coincidental.

Key Points

• Comparison Tool: Use to compare loans/investments with different compounding frequencies.
• Limitations: Assumes reinvestment at the same rate; does not account for fees or irregular payments.