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LN Function

Excel 2007+

Summary

The Excel LN function calculates the natural logarithm of a positive number, using base e (approximately 2.71828). This is a fundamental mathematical operation essential for growth modeling, scientific calculations, and advanced financial analysis.

Syntax

LN(number)

Parameters

Parameter	Type	Required	Description
number	`Number`	Yes	A positive real number (>0) for which you want the natural logarithm

Using the LN Function

Use LN for financial modeling (continuous compounding), scientific calculations, statistical analysis, and any scenario involving exponential growth or decay. It's particularly valuable when working with e-based exponential functions.

Common LN Examples

Basic Natural Logarithm

=LN(86)

Returns 4.4543473, the natural log of 86

Constant e Verification

=LN(2.7182818)

Returns approximately 1, verifying the base e constant

Inverse of EXP Function

=LN(EXP(3))

Returns exactly 3, demonstrating LN as inverse of EXP

Frequently Asked Questions

LN returns a #NUM! error for negative numbers or zero since natural log is undefined for non-positive values.

LN uses base e (natural log), while LOG lets you specify any base (like 10 for common log).

Yes, LN works with Excel's full numeric range but input must remain positive.

Common Errors and Solutions

#NUM! Error

Cause: Number argument is negative, zero, or non-numeric

Solution: Ensure input is a positive number greater than 0

Notes

Natural log base is e = 2.71828182845904
LN(1) always equals 0
LN(e^x) = x for any x
Available in all Excel versions since 2007

Compatibility

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

Not available in:

Content last reviewed: December 11, 2025
Update frequency: As needed
Excel versions tested: Excel 2007+