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IMSUM Function

Excel 2007+

Summary

The IMSUM function adds two or more complex numbers together, handling both real and imaginary components. Complex numbers are expressed in Excel as text strings in the format 'x+yi' or 'x+yj' where x is the real part and y is the imaginary part.

Syntax

IMSUM(inumber1, [inumber2], ...)

Parameters

Parameter	Type	Required	Description
inumber1	`Complex`	Yes	First complex number (required) - format: x+yi or x+yj
[inumber2], ...	`Complex`	No	Additional complex numbers (optional) - up to 254 more, total 255 max

Using the IMSUM Function

IMSUM is perfect for complex number calculations in engineering, physics, and mathematics applications within Excel. Use it when you need to sum multiple complex values from formulas, data tables, or calculations involving the COMPLEX function.

Common IMSUM Examples

Basic Two-Number Sum

=IMSUM("3+6i","5-2i")

Adds 3+6i and 5-2i to get 8+4i (real: 3+5=8, imaginary: 6-2=4)

Summing Three Complex Numbers

=IMSUM("1+2i", "3-1i", "-2+4i")

Sums three complex numbers: real parts (1+3-2=2), imaginary parts (2-1+4=5) = 2+5i

Using with COMPLEX Function

=IMSUM(COMPLEX(4,3), COMPLEX(2,-1))

Converts real/imaginary pairs to complex numbers then sums them

Frequently Asked Questions

Use text format like "3+4i" or "5-2j". Use COMPLEX(real_num, i_num) to create them from numeric values.

Yes, use minus sign like "5-3i" for 5 minus 3i.

Up to 255 complex numbers can be added in a single IMSUM formula.

Common Errors and Solutions

#VALUE! error

Cause: Invalid complex number format (wrong syntax)

Solution: Use correct format: real+imaginaryi (e.g., "3+4i") or COMPLEX function

#NUM! error

Cause: Coefficients too large for Excel

Solution: Verify numbers are within Excel's precision limits

Too many arguments

Cause: More than 255 complex numbers provided

Solution: Split into multiple IMSUM formulas

Notes

IMSUM only works with complex numbers - use regular SUM for real numbers
Use COMPLEX(4,3) to create complex numbers from separate real/imaginary values
Result is returned as text in x+yi format
Available in Excel 2007 and later versions

Compatibility

Available in: Excel 2007, Excel 2010, Excel 2013, Excel 2016, Excel 2019, Excel 2021, Excel for Microsoft 365

Not available in: Excel 2003, Excel XP, Excel 2000, Excel 97

Content last reviewed: December 9, 2025
Update frequency: As needed
Excel versions tested: Excel 2007+