Excel LOG function


The Excel LOG function calculates the logarithm of a number to a specified base. This function is useful in various fields, including mathematics, science, and finance, where understanding the rate of change or growth is essential. Unlike the LN function, which calculates the natural logarithm, LOG allows you to specify any base for the logarithm calculation.
					=LOG(number, [base])
  • number: The positive numeric value for which you want to calculate the logarithm
  • [base]: [Optional] The base of the logarithm. If omitted, the default base is 10
Return value
The logarithm of the number to the specified base.

How to use

Use LOG by entering the number and optionally specifying the base. If the base is not specified, LOG uses a default base of 10 (common logarithm).


Simple LOG
Calculating Logarithm to Base 10: Finding the common logarithm (base 10) of a number:
This formula calculates the base-10 logarithm of 100, resulting in 2.
LOG with Specified Base
Logarithm to a Specific Base: Calculating the logarithm with a specified base:
					=LOG(8, 2)
Calculates the logarithm of 8 to base 2, resulting in 3.
LOG in Scientific Analysis
Analyzing Scientific Data: Using LOG for scientific data involving different bases:
					=LOG(A2, e)
Assuming A2 contains a value, and ‘e’ is the mathematical constant, this formula calculates the logarithm to the base e (natural logarithm).
LOG for Financial Modeling
Compound Interest Calculations: Applying LOG in compound interest calculations:
					=LOG(Final_Value / Initial_Value, Rate)
Calculates the logarithm of the ratio of final to initial value at a specified rate, often used in compound interest calculations.
LOG in Complex Formulas
Integrating LOG in Advanced Calculations: Combining LOG with other Excel functions:
					=LOG(1 + Annual_Interest_Rate) / LOG(2)
This calculates the logarithm of 1 plus an annual interest rate to the base 2.

Additional Notes

  • LOG is versatile and essential in various applications, especially where understanding logarithmic relationships is crucial.
  • It’s important that the number for which you’re calculating the logarithm is positive, as logarithms of zero or negative numbers are undefined.

Related Functions

Excel EXP function

The Excel EXP function calculates the exponential value of a number, e^n, crucial for growth calculations and logarithmic reversals.

Excel LN function

The Excel LN function calculates the natural logarithm of a number, essential for growth rate and time series analysis.

Excel LOG10 function

The Excel LOG10 function calculates the base-10 logarithm of a number, fundamental for scientific data scaling and normalization.

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