Engineering

COMPLEX Function in Excel

Converts real and imaginary coefficients into a complex number.

Syntax

  • =COMPLEX(real_num, i_num, [suffix])

Arguments

  • real_num (required): Real coefficient
  • i_num (required): Imaginary coefficient
  • suffix (optional): Suffix for imaginary (i or j)

Examples

  • =COMPLEX(3, 4) - Create complex number - Result: 3+4i

COMPLEX in technical sheets

  • Document units in adjacent cells — many engineering functions require exact unit strings.
  • Use [CONVERT](/functions/convert/) for unit changes before specialized formulas.
  • Validate inputs with [ISNUMBER](/functions/isnumber/) and range checks.

Common errors

  • Suffix must be i or j

Use cases

  • Complex math
  • Engineering calculations
  • Signal processing

Frequently asked questions

  • How do I work with complex numbers in Excel? Create complex numbers with COMPLEX(real, imaginary). Use IM functions for operations: IMSUM for addition, IMSUB for subtraction, IMPRODUCT for multiplication, IMDIV for division. Complex numbers are stored as text like "3+4i".
  • What is the difference between 'i' and 'j' suffix? Both represent the imaginary unit (√-1). Mathematicians use 'i', engineers often use 'j' (since 'i' means current in electrical engineering). Use =COMPLEX(3, 4, "j") for engineering notation: "3+4j".
  • How do I calculate the magnitude of a complex number? Use IMABS: =IMABS("3+4i") returns 5. This is the distance from origin: √(real² + imaginary²). For 3+4i: √(9+16) = √25 = 5. Also called modulus or absolute value.

Editorial review

  • Reviewed by Excel.Directory Editorial Team. Updated May 2026.