What is a lookup function in excel

This Excel tutorial explains how to use the Excel LOOKUP function with syntax and examples.

Description

The Microsoft Excel LOOKUP function returns a value from a range (one row or one column) or from an array.

The LOOKUP function is a built-in function in Excel that is categorized as a Lookup/Reference Function. It can be used as a worksheet function (WS) in Excel. As a worksheet function, the LOOKUP function can be entered as part of a formula in a cell of a worksheet.

There are 2 different syntaxes for the LOOKUP function:

LOOKUP Function (Syntax #1)

In Syntax #1, the LOOKUP function searches for value in the lookup_range and returns the value in the result_range that is in the same position.

The syntax for the LOOKUP function in Microsoft Excel is:

LOOKUP( value, lookup_range, [result_range] )

Parameters or Arguments

value

The value to search for in the lookup_range.

lookup_range

A single row or single column of data that is sorted in ascending order. The LOOKUP function searches for value in this range.

result_range

Optional. It is a single row or single column of data that is the same size as the lookup_range. The LOOKUP function searches for the value in the lookup_range and returns the value from the same position in the result_range. If this parameter is omitted, it will return the first column of data.

Returns

The LOOKUP function returns any datatype such as a string, numeric, date, etc.
If the LOOKUP function can not find an exact match, it chooses the largest value in the lookup_range that is less than or equal to the value.
If the value is smaller than all of the values in the lookup_range, then the LOOKUP function will return #N/A.
If the values in the LOOKUP_range are not sorted in ascending order, the LOOKUP function will return the incorrect value.

Example (as Worksheet Function)

Let’s look at some Excel LOOKUP function examples and explore how to use the LOOKUP function as a worksheet function in Microsoft Excel:

Based on the Excel spreadsheet above, the following LOOKUP examples would return:

=LOOKUP(10251, A1:A6, B1:B6)
Result: "Pears"

=LOOKUP(10251, A1:A6)
Result: 10251

=LOOKUP(10246, A1:A6, B1:B6)
Result: #N/A

=LOOKUP(10248, A1:A6, B1:B6)
Result: "Apples"

LOOKUP Function (Syntax #2)

In Syntax #2, the LOOKUP function searches for the value in the first row or column of the array and returns the corresponding value in the last row or column of the array.

The syntax for the LOOKUP function in Microsoft Excel is:

LOOKUP( value, array )

Parameters or Arguments

value

The value to search for in the array. The values must be in ascending order.

array

An array of values that contains both the values to search for and return.

Returns

The LOOKUP function returns any datatype such as a string, numeric, date, etc.
If the LOOKUP function can not find an exact match, it chooses the largest value in the lookup_range that is less than or equal to the value.
If the value is smaller than all of the values in the lookup_range, then the LOOKUP function will return #N/A.
If the values in the array are not sorted in ascending order, the LOOKUP function will return the incorrect value.

Example (as Worksheet Function)

Let’s look at some Excel LOOKUP function examples and explore how to use the LOOKUP function as a worksheet function in Microsoft Excel:

=LOOKUP("T", {"s","t","u","v";10,11,12,13})
Result: 11

=LOOKUP("Tech on the Net", {"s","t","u","v";10,11,12,13})
Result: 11

=LOOKUP("t", {"s","t","u","v";"a","b","c","d"})
Result: "b"

=LOOKUP("r", {"s","t","u","v";"a","b","c","d"})
Result: #N/A

=LOOKUP(2, {1,2,3,4;511,512,513,514})
Result: 512

Frequently Asked Questions

Question: In Microsoft Excel, I have a table of data in cells A2:D5. I’ve tried to create a simple LOOKUP to find CB2 in the data, but it always returns 0. What am I doing wrong?

Answer: Using the LOOKUP function can sometimes be a bit tricky so let’s look at an example. Below we have a spreadsheet with the data that you described.

In cell F1, we’ve placed the following formula:

=LOOKUP("CB2",A2:A5,D2:D5)

And yes, even though CB2 exists in the data, the LOOKUP function returns 0.

Now, let’s explain what is happening. At first, it looks like the function isn’t finding CB2 in the list, but in fact, it is finding something else. Let’s fill in the empty cells in D3:D5 to explain better.

If we place the values TEST1, TEST2, TEST3 in cells D3, D4, 5, respectively, we can see that the LOOKUP function is in fact returning the value TEST2. So we ask ourselves, when we are looking up CB2 in the data and CB2 exists in the data, why is it returning the value for CB19? Good question. The LOOKUP function assumes that the data in column A is sorted in ascending order.

If you look closer at column A, it is not in fact sorted in ascending order. If we quickly sorted column A, it would look like this:

Now the LOOKUP function correctly returns 3A when it is looking up CB2 in the data.

To avoid these sorting problems with your data, we recommend using VLOOKUP function in this case. Let’s show you how we would do this. If we changed our formula below (but left our data in column A in the original sort order):

The following VLOOKUP formula would return the correct value of 3A.

=VLOOKUP("CB2",$A$2:$D$5,4,FALSE)

The VLOOKUP function does not require us to have the data sorted in ascending order since we used FALSE as the last parameter — which means that it is looking for an exact match.

Question: I have the following LOOKUP formula:

=LOOKUP(C2,{"A","B","C","D","E","F","G","H","I","K","X","Z"}, {"1","2","3","4","5","6","7","8","9","10","12","1"})

I also need to add zero to the lookup vector and result vector. How do I do this?

Answer: Using numbers in Excel can be tricky, as you can enter them either as numeric or text values. Because of this, there are 2 possible solutions.

Numeric Solution

If you have entered your zero as a numeric value, then the following formula will work:

=LOOKUP(C2,{0,"A","B","C","D","E","F","G","H","I","K","X","Z"}, {0,"1","2","3","4","5","6","7","8","9","10","12","1"})

Text Solution

If you have entered your zero as a text value, then the following formula will work:

=LOOKUP(C2,{"0","A","B","C","D","E","F","G","H","I","K","X","Z"}, {"0","1","2","3","4","5","6","7","8","9","10","12","1"})

Question: For the following function in Microsoft Excel:

=LOOKUP(M14,Sheet2!A2:A2240,Sheet2!B2:B2240)

How do I get it to return a blank cell if the LOOKUP value (M14) is blank?

Answer: To check for a blank value in cell M14, you can use the IF function and ISBLANK function as follows:

=IF(ISBLANK(M14),"",LOOKUP(M14,Sheet2!A2:A2240,Sheet2!B2:B2240))

Now if the value in cell M14 is blank, the formula will return a blank. Otherwise it will perform the LOOKUP function as before.

Use the LOOKUP function to look up a value in a one-column or one-row range, and retrieve a value from the same position in another one-column or one-row range. The lookup function has two forms, vector and array. The majority of this article describes the vector form, but the last example below illustrates the array form.

The LOOKUP function accepts three arguments: lookup_value, lookup_vector, and result_vector. The first argument, lookup_value, is the value to look for. The second argument, lookup_vector, is a one-row, or one-column range to search. LOOKUP assumes that lookup_vector is sorted in ascending order. The third argument, result_vector, is a one-row, or one-column range of results. Result_vector is optional. When result_vector is provided, LOOKUP locates a match in the lookup_vector, and returns the corresponding value from result_vector. If result_vector is not provided, LOOKUP returns the value of the match found in lookup_vector.

LOOKUP has default behaviors that make it useful when solving certain problems. For example, LOOKUP can be used to retrieve an approximate-matched value instead of a position and to find the last value in a row or column. LOOKUP assumes that values in lookup_vector are sorted in ascending order and always performs an approximate match. When LOOKUP can’t find a match, it will match the next smallest value.

Example #1 — basic usage

In the example shown above, the formula in cell F5 returns the value of the match found in column B. Note that result_vector is not provided:

=LOOKUP(F4,B5:B9) // returns match in level

The formula in cell F6 returns the corresponding Tier value from column C. Notice in this case, both lookup_vector and result_vector are provided:

=LOOKUP(F4,B5:B9,C5:C9) // returns corresponding tier 

In both formulas, LOOKUP automatically performs an approximate match and it is therefore important that lookup_vector is sorted in ascending order.

Example #2 — last non-empty cell

LOOKUP can be used to get the value of the last filled (non-empty) cell in a column. In the screen below, the formula in F6 is:

=LOOKUP(2,1/(B:B<>""),B:B)

Note the use of a full column reference. This is not an intuitive formula, but it works well. The key to understanding this formula is to recognize that the lookup_value of 2 is deliberately larger than any values that will appear in the lookup_vector. Detailed explanation here.

Example #3 — latest price

Similar to the above example, the lookup function can be used to look up the latest price in data sorted in ascending order by date. In the screen below, the formula in G5 is:

=LOOKUP(2,1/(item=F5),price)

where item (B5:B12) and price (D5:D12) are named ranges. 

When lookup_value is greater than all values in lookup_array, default behavior is to «fall back» to the previous value. This formula exploits this behavior by creating an array that contains only 1s and errors, then deliberately looking for the value 2, which will never be found. More details here.

Example #4 — array form

The LOOKUP function has an array form as well. In the array configuration, LOOKUP takes just two arguments: the lookup_value, and a single two-dimensional array:

LOOKUP(lookup_value, array) // array form

In the array form, LOOKUP evaluates the array and automatically changes behavior based on the array dimensions. If the array is wider than tall, LOOKUP looks for the lookup value in the first row of the array (like HLOOKUP). If the array is taller than wide (or square), LOOKUP looks for the lookup value in the first column (like VLOOKUP). In either case, LOOKUP returns a value at the same position from the last row or column in the array. The example below shows how the array form works. The formula in F5 is configured to use a vertical array and the formula in F6 is configured to use a horizontal array:

=LOOKUP(E5,B5:C9) // vertical array
=LOOKUP(E6,C11:G12) // horizontal array

The vertical and horizontal arrays contain the same values; only the orientation is different.

Note: Microsoft discourages the use of the array form and suggests VLOOKUP and HLOOKUP as better options.

Notes

• LOOKUP assumes that lookup_vector is sorted in ascending order.
• When lookup_value can’t be found, LOOKUP will match the next smallest value.
• When lookup_value is greater than all values in lookup_vector, LOOKUP matches the last value.
• When lookup_value is less than the first value in lookup_vector, LOOKUP returns #N/A.
• Result_vector must be the same size as lookup_vector.
• LOOKUP is not case-sensitive