# LOGEST function: Description, Usage, Syntax, Examples and Explanation

## What is LOGEST function in Excel?

LOGEST function is one of Statistical functions in Microsoft Excel that r
In regression analysis, calculates an exponential curve that fits your data and returns an array of values that describes the curve. Because this function returns an array of values, it must be entered as an array formula.The equation for the curve is:

y = b*m^x

or

y = (b*(m1^x1)*(m2^x2)*_)

if there are multiple x-values, where the dependent y-value is a function of the independent x-values. The m-values are bases corresponding to each exponent x-value, and b is a constant value. Note that y, x, and m can be vectors. The array that LOGEST returns is {mn,mn-1,…,m1,b}.

## Syntax of LOGEST function

LOGEST(known_y’s, [known_x’s], [const], [stats])

The LOGEST function syntax has the following arguments:

• Known_y’s    Required. The set of y-values you already know in the relationship y = b*m^x.
• If the array known_y’s is in a single column, then each column of known_x’s is interpreted as a separate variable.
• If the array known_y’s is in a single row, then each row of known_x’s is interpreted as a separate variable.
• Known_x’s    Optional. An optional set of x-values that you may already know in the relationship y = b*m^x.
• The array known_x’s can include one or more sets of variables. If only one variable is used, known_y’s and known_x’s can be ranges of any shape, as long as they have equal dimensions. If more than one variable is used, known_y’s must be a range of cells with a height of one row or a width of one column (which is also known as a vector).
• If known_x’s is omitted, it is assumed to be the array {1,2,3,…} that is the same size as known_y’s.
• Const    Optional. A logical value specifying whether to force the constant b to equal 1.
• If const is TRUE or omitted, b is calculated normally.
• If const is FALSE, b is set equal to 1, and the m-values are fitted to y = m^x.
• Stats    Optional. A logical value specifying whether to return additional regression statistics.
• If stats is TRUE, LOGEST returns the additional regression statistics, so the returned array is {mn,mn-1,…,m1,b;sen,sen-1,…,se1,seb;r 2,sey; F,df;ssreg,ssresid}.
• If stats is FALSE or omitted, LOGEST returns only the m-coefficients and the constant b.

## LOGEST formula explanation

• The more a plot of your data resembles an exponential curve, the better the calculated line will fit your data. Like LINEST, LOGEST returns an array of values that describes a relationship among the values, but LINEST fits a straight line to your data; LOGEST fits an exponential curve. For more information, see LINEST.
• When you have only one independent x-variable, you can obtain y-intercept (b) values directly by using the following formula:Y-intercept (b):
INDEX(LOGEST(known_y’s,known_x’s),2)You can use the y = b*m^x equation to predict future values of y, but Microsoft Excel provides the GROWTH function to do this for you. For more information, see GROWTH function.
• Formulas that return arrays must be entered as array formulas.

Note:  In Excel Online you cannot create array formulas.

• When entering an array constant such as known_x’s as an argument, use commas to separate values in the same row and semicolons to separate rows. Separator characters may be different depending on your regional settings.
• You should note that the y-values predicted by the regression equation may not be valid if they are outside the range of y-values you used to determine the equation.

## Example of LOGEST function

### Example 1

Steps to follow:

1. Open a new Excel worksheet.

2. Copy data in the following table below and paste it in cell A1

Note: For formulas to show results, select them, press F2 key on your keyboard and then press Enter.

You can adjust the column widths to see all the data, if need be.

 Month Units 11 33100 12 47300 13 69000 14 102000 15 150000 16 220000 Formula Description Result =LOGEST(B2:B7,A2:A7, TRUE, FALSE) Note The formula in the example must be entered as an array formula in the Excel program. After copying the example to a blank worksheet, select the range C9:D9 starting with the formula cell. Press F2, and then press CTRL+SHIFT+ENTER. If the formula is not entered as an array formula, the single result is 1.4633. 1.4633 495.3048

### Example 2

Copy the example data in the following table, and paste it in cell A1 of a new Excel worksheet. For formulas to show results, select them, press F2, and then press Enter. If you need to, you can adjust the column widths to see all the data.

 Month Units 11 33,100 12 47,300 13 69,000 14 102,000 15 150,000 16 220,000 Formula Result =LOGEST(B2:B7,A2:A7,TRUE,TRUE) 1.4633