EFFECT Function in Apple Numbers: Syntax and Worked Examples

• Introduced: Documented in Apple’s Formulas and Functions Help 15.4; the first release and introduction date remain unknown.
• Availability: Currently documented for Numbers in that 15.4 documentation edition; it does not establish a final supported-version endpoint.
• Scope: Shared iWork function reference. Client-specific introduction dates and older Mac, iPad, iPhone and iCloud behavior are not established here.
• Checked: October 14, 2026, against the official EFFECT reference. Documentation and independent arithmetic checks; no native Numbers test.

=EFFECT(nominal-rate, num-periods-year)

Both arguments are required numbers. Enter the nominal annual rate as a percentage or its decimal equivalent: 6% and 0.06 mean the same thing. The second argument is the number of compounding periods in one year, and Apple’s reference requires it to be greater than zero.

For ordinary positive rates and whole-number frequencies, the compound-growth calculation is:

(1 + nominal annual rate / periods per year) ^ periods per year - 1

A monthly frequency is 12, quarterly is 4, and annual is 1. The argument is not the number of years in the investment. EFFECT has no term-length, principal, fee, deposit or withdrawal argument.

Use English function names and comma separators for the formulas shown. Adapt separators to the document’s locale if necessary. Format rate inputs and outputs as percentages; a decimal result such as 0.0616778 means about 6.16778%, not 0.0616778%.

Create a blank table with at least columns A:F and eight rows. Put Nominal annual rate, Periods/year, Effective annual rate, and Direct calculation in A1:D1. Enter these values in A2:B8:

In C2, enter =EFFECT(A2,B2) and fill through C8. In D2, enter =(1+A2/B2)^B2-1 and fill through D8. Display C:D as percentages with eight decimal places. The two columns should agree to the displayed precision for these cases.

The annual-compounding row returns the original 6%. With the same positive nominal rate, more frequent reinvestment increases the effective rate. Row 6 models exactly 365 equal compounding periods; the formula does not inspect a calendar or automatically substitute 366 in a leap year.

To check the reverse conversion, put =NOMINAL(C5,B5) in F5. It gives 6%, using the unrounded effective rate stored in C5. The NOMINAL function performs that inverse conversion. Do not replace C5 with its rounded printed percentage when testing the identity.

Create a separate table named Offers, with six columns A:F and three rows. Set the headers to Offer, Nominal rate, Periods/year, Effective rate, Opening amount, and One-year balance.

Enter =EFFECT(B2,C2) in D2 and fill to D3. Enter =E2*(1+D2) in F2 and fill to F3. Expected one-year balances are 10,616.78 and 10,610.00, displayed to two decimals. The unrounded difference is approximately 6.778118645 currency units.

Although the monthly model’s nominal rate is lower, its effective rate is higher in this controlled example. The comparison assumes an unchanged rate, reinvestment at each compounding date and no intervening cash flows, taxes or fees. It does not determine which real account or borrowing arrangement is preferable.

In a new table named MonthlyCheck, create at least two columns (A:B) and fourteen rows. Use headers Month and Balance in A1:B1. Put 0 in A2 and 10000 in B2. In A3 enter =A2+1 and fill through A14. In B3 enter =B2*(1+6%/12) and fill through B14.

B14 is the balance after twelve monthly steps: approximately 10,616.778118645. It agrees with the first offer’s annual calculation. Keep full precision in the stored formulas; formatting to two decimals is different from rounding each month’s amount before the next step. For models with regular additional cash flows, use an appropriate function such as FV rather than expecting EFFECT to account for them.

• Entering 6 instead of 6% supplies a 600% nominal annual rate.
• Do not pass the monthly rate into EFFECT as though it were already annual. Multiply a genuinely nominal periodic rate by its stated yearly frequency first.
• Use a positive whole-number frequency for this workflow. Apple’s short entry does not specify how fractional frequencies are handled; do not import another spreadsheet’s truncation rule.
• The entry does not enumerate exact error tokens or the full zero/negative-rate domain. Verify those cases in the intended client rather than assuming Excel’s constraints.
• An effective annual rate is not a complete contractual APR calculation. Charges and legal disclosure conventions may require additional inputs and rules.