In this Article

*This Tutorial demonstrates how to use the Excel LOG Function in Excel to calculate the logarithm of a number to a specified base.*

## LOG Function Overview

The LOG Function Calculates the logarithm of a number to a specified base.

To use the LOG Excel Worksheet Function, select a cell and type:

(Notice how the formula inputs appear)

## LOG Function Syntax and Inputs:

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=LOG(number,base) |

**number** – A number.

**base** – OPTIONAL. The base of the logarithm. Blank as default.

**LOG Function **

The LOG Function returns the logarithm of a number to the specified base.

1 |
=LOG(64,4) |

**LOG Function – Base 10**

The LOG Function will return the logarithm of a number to base 10 if the second argument is omitted.

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=LOG(1000) |

Alternatively, the LOG10 Function can also be used. To learn more, click here.

**LOG Function – Base ‘e’**

The LOG Function can return the logarithm of a number to base ‘e’.

1 |
=LOG(5, EXP(1)) |

Alternatively, the LN Function can also be used. To learn more, click here.

**LOG & POWER Function**

The LOG Function is a reverse of the POWER Function. The LOG Function returns the power to which the given base was raised.

Let’s say we raise 7 to the power of 3.

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=POWER(7,3) |

The resulting number when entered in the LOG Function to the base 7 will return the power.

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=LOG(343,7) |

To learn more about the POWER Function, click here.

**LOG Function – Negative Number/Zero**

The LOG Function will return an error if the argument is zero or a negative number.

1 |
=LOG(0) |

1 |
=LOG(-5) |

**LOG** in Google Sheets

The LOG Function works exactly the same in Google Sheets as in Excel:

## Additional Notes

Use the LOG Function to calculate the logarithm of a number to a specified base. Simply enter any number directly into the formula, or reference a cell containing a number.

## LOG Examples in VBA

You can also use the LOG function in VBA. Type:

`application.worksheetfunction.log(number,base)`

For the function arguments (number, etc.), you can either enter them directly into the function, or define variables to use instead.

Return to the List of all Functions in Excel