Engineering

IMSUM Function in Excel

Returns the sum of complex numbers.

Syntax

  • =IMSUM(inumber1, [inumber2], ...)

Arguments

  • inumber1 (required): First complex number
  • inumber2 (optional): Additional complex numbers

Examples

  • =IMSUM("3+4i", "1+2i") - Add complex numbers - Result: 4+6i

IMSUM 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

  • #NUM! if not valid complex numbers

Use cases

  • Complex arithmetic
  • Engineering
  • Signal processing

Frequently asked questions

  • What is the IMSUM function in Excel? IMSUM returns the sum of complex numbers. The syntax is =IMSUM(inumber1, [inumber2], ...). Typical use cases include complex arithmetic, engineering, signal processing.
  • How do I use the IMSUM function? To use IMSUM, type =IMSUM( in a cell and provide the required arguments. Excel will show you the syntax and parameter hints as you type. Make sure to close the parentheses and press Enter to execute the function.
  • Why is IMSUM not working in my Excel? Common issues with IMSUM include #NUM! if not valid complex numbers. Start by checking the syntax =IMSUM(inumber1, [inumber2], ...), then verify each referenced cell or range.

Editorial review

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