BESSELI Function

Excel Functions › Engineering

All versions Engineering

The Excel BESSELI function returns the modified Bessel function In(x) — for engineering and physics problems with cylindrical symmetry.

Quick answer:
=BESSELI(1.5, 1) // order-1 value at x = 1.5

Syntax

=BESSELI(x, n)
ArgumentDescription
xRequiredThe value at which to evaluate the function.
nRequiredThe order of the Bessel function (a non-negative integer).

How to use it

BESSELI returns the modified Bessel function In(x) — a special function that appears in physics and engineering problems with cylindrical symmetry (wave propagation, heat conduction, vibrations, signal processing).

=BESSELI(1.5, 1) // order-1 value at x = 1.5

Order n must be a non-negative integer (it is truncated if not). The four Bessel functions pair up: J and Y are the standard solutions; I and K are their modified (exponential-growth) counterparts.

Try it: interactive demo

Live demo

Set x and the order n to see the formula BESSELI evaluates.

Result: a value computed in Excel

Practice workbook

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Frequently asked questions

What is the order argument n?
The order of the Bessel function (J0, J1, J2…). It must be a non-negative integer; non-integers are truncated.
Which Excel versions have Bessel functions?
All modern versions include them (they ship with the core install, no add-in needed).
Where are Bessel functions used?
Problems with cylindrical or spherical symmetry: vibrating membranes, waveguides, heat flow in pipes, FM signal spectra.
Why #NUM! or #VALUE!?
#VALUE! if x or n isn’t numeric; #NUM! if n is negative.

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Related functions: CONVERT · DELTA · ERF · BESSELJ