The Excel LOOKUP Function

Related Functions:

HLOOKUP Function

VLOOKUP Function


Basic Description

The Excel Lookup function has two forms - the Vector form and the Array form. These are described individually below.


The Vector Form of the Excel Lookup Function

The vector form of the Lookup function 'looks up' a value in a data vector (ie. a 1-dimensional list of data) and returns the corresponding value from a second data vector.

The format of the function is :

LOOKUP( lookup_value, lookup_vector, [result_vector] )

Where the arguments are as follows :

lookup_value - The value that you want to look up.
lookup_vector - A 1-dimensional list of data, which you want to search through, for the lookup_value.
[result_vector] -

An optional 1-dimensional list of data, from which you want to return a value.

If supplied, the [result_vector] must be the same length as the lookup_vector.

If the [result_vector] is omitted, the result is returned from the lookup_vector.


Example of the Vector Form of the Excel Lookup Function

In the spreadsheet below, cells A1-E3 relate to a variable interest rate, that is paid on a bank account. For balances of 0-$999.99, the interest rate is 3%, for balances of $1000-$1,999.99, the interest rate is 4%, etc.

Cell A6 of the spreadsheet shows the balance of a specific bank account and cell B6 shows the vector form of the Excel Lookup function being used to look up the interest rate relating to this balance.

  A B C D E
1 Lower Balance $0.00 $1,000.00 $10,000.00 $50,000.00
2 Upper Balance $999.99 $9,999.99 $49,999.99  
3 Interest Rate 3% 4% 5% 6%
4          
5 Acct Balance: Interest Rate:    
6 $45,000.00 =LOOKUP( A7, B1:E1, B3:E3 )  

The Lookup function in cell B6 of the above spreadsheet returns the interest rate of 5%, which is the correct interest rate to apply to a bank account with a balance of $45,000.

In this example:

  -    the lookup_value is the value $45,000.00, which is located in cell A6
  -    the lookup_vector is the vector of data in cells B1-E1 of the spreadsheet
  -    the [result_vector] is the vector of data in cells B3-E3 of the spreadsheet.

Note that the vector form of the Excel Lookup function can be used with any two arrays of data that have one-on-one matching values. For example, two columns of data, two rows of data, or even a column and a row would work, as long as the lookup_vector is ordered (alphabetically or numerically), and the two data sets are the same length.



The Array Form of the Excel Lookup Function

The array form of the Lookup function 'looks up' a supplied value in the first column or row of a supplied data array (ie. a 2-dimensional table of data) and returns the corresponding value from the last column or row of the array.

The format of the function is :

LOOKUP( lookup_value, array )

Where the arguments are as follows :

lookup_value - The value that you want to look up.
array - A 2-dimensional array (or table) of data, containing values to be searched in the first row or column and values to be returned in the last row or column.


Example of the Array Form of the Lookup Function

In the spreadsheet below, columns A-C list the grades that are assigned to examination marks lying within the ranges 0-44%, 45%-54%, etc.

Cell F2 shows the score of 82% that was achieved by the student "Chris" in an examination. The Lookup function in cell G2 looks up this score in column A of the spreadsheet and returns the associated grade from column C. Note that, in this example, if the exact score of 82% is not found in column A, we want the function will use the nearest value below this score.

  A B C D E F G
1 Lower Upper Grade   Name Score Grade
2 0% 44% F   Chris 82% =LOOKUP( F2, A2:C7 )
3 45% 54% E        
4 55% 64% D        
5 65% 74% C        
6 75% 84% B        
7 85% 100% A        

The above Lookup function returns the grade for the score 82%, which is B.

In this example:

  -    the lookup_value is the value 82%, which is located in cell F2
  -    the array is the vector of data in cells A2-C7 of the spreadsheet.

Note: In this example, the Excel Lookup function recognised that it was searching for the lookup_value in the first column of the supplied array, and returning a value from the last column. However if the array is transposed so that the data runs across 3 rows, the function will recognise this, and will still return the correct values.


Further Lookup Function Examples

Further examples of the Excel Lookup function can be found on the Microsoft Office website.


Excel Lookup Function Errors

If you get an error from the Excel Lookup function this is likely to be the following :

Common Errors
#N/A - This error indicates that the Lookup function fails to find a closest match to the supplied lookup_value. This is usually because the smallest value in the lookup_vector (or first column/row of the array) is greater than the supplied lookup_value.

Also, the following problem is encountered by some users:

Common Lookup Problem

Your Excel Lookup function is returning the wrong value

Possible Reason No. 1

This problem may arise if the data in the lookup_vector or in the first row or column of the supplied array, is not ordered, (alphabetically or in ascending numerical order).

Solution No. 1

Try ordering the data by the lookup_vector (for the vector form of the function) or, if using the array form of the function, order by the first row or column of the supplied array. If your data is organised into columns rather than rows, the ordering can be done using the Sort... option in the Data menu.

If your Excel Lookup function still returns the wrong result, check that your supplied lookup range(s) contain ONLY the data you want to search. (eg. if you have used the whole of columns A-C as a supplied array, change this to omit your headings and also to omit any other data that might be further down the spreadsheet).

Possible Reason No. 2

You may have unseen spaces at the start or end of either the value you are looking up, or in the cells of your lookup_vector or array. These spaces cause your lookup_value cell and the 'matching' cell in your lookup_vector or table_array to have slightly different content.

Solution No. 2
Check the contents of the cells that you believe should match. If there are unseen additional spaces in one or both of the lists, remove these using the TRIM function:
  1. Create a new column next to the one with the additional spaces in it
  2. Use the TRIM function in your new column, to get rid of extra spaces
  3. Copy the contents of the new column and paste these over the top of the original column, using paste->special->values
  4. Delete the column containing the TRIM function
Possible Reason No. 3

The contents of the cells that are being compared may have different data types. For example, the cell containing your lookup_value may be stored as a number by Excel, whereas the values in your table_array may be stored as text even though they look like numbers.

Solution No. 3
Force both sets of data to have the same type. For example, if you want both sets of values to be stored as numerical values, convert both sets of data to numbers, using Excel's Text To Columns tool:
  1. Use the mouse to select the cells you want to convert to text (this must not span more than one column)
  2. From the Data tab at the top of your Excel workbook, select the Text to Columns ... option
  3. Make sure the Delimited option is selected and click next
  4. Make sure all the delimiter options are unselected and then click next again
  5. You should now be offered a selection of Column Data Formats. Select General and click the Finish button

Note that you could have chosen to convert the contents of your cells to text, by simply selecting the column data format Text in the Text To Columns tool.

Once you have ensured that your data has the correct type, check again that it is ordered correctly. This is important because Excel uses different ordering rules for text strings made up of numbers, compared to those used for numerical values.

Possible Reason No. 4

You may not actually require the function to return a closest match - you may only want a result if an exact match is found. In this case, the Excel Lookup function is not the correct function to use.

Solution No. 4

Try using the Vlookup Function or the Hlookup Function instead!

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