by Svetlana Cheusheva, updated on

*The tutorial explains the vector and array forms of the Excel LOOKUP function and demonstrates typical and non-trivial uses of LOOKUP in Excel with formula examples.*

One of the most frequent questions that every Excel user asks once in a while is this: "*How do I look up a value on one sheet and pull a matching value to another sheet?*". Of course, there can be many variations of the basic scenario: you may be looking for the closest match rather than exact match, you may want to search vertically in a column or horizontally in a row, evaluate one or multiple criteria, etc. However, the essence is the same - you need to know how to look up in Excel.

Microsoft Excel provides a handful of different ways to do lookup. To begin with, let's learn a function that is designed to handle the simplest cases of vertical and horizontal lookup. As you can easily guess, I am talking about the LOOKUP function.

At the most basic level, the LOOKUP function in Excel searches a value in one column or row and returns a matching value from the same position in another column or row.

There are two forms of LOOKUP in Excel: **Vector** and **Array**. Each form is explained individually below.

In this context, a *vector* refers to a one-column or one-row range. Consequently, you use the vector form of LOOKUP to search one row or one column of data for a specified value, and pull a value from the same position in another row or column.

The syntax of the vector Lookup is as follows:

LOOKUP(lookup_value, lookup_vector, [result_vector])

Where:

**Lookup_value**(required) - a value to search for. It can be a number, text, logical value of TRUE or FALSE, or a reference to a cell containing the lookup value.**Lookup_vector**(required) - one-row or one-column range to be searched. It must be sorted in**ascending order**.**Result_vector**(optional) - one-row or one-column range from which you want to return the result - a value in the same position as the lookup value.*Result_vector*must be the**same size**as*lookup_range*. If omitted, the result is returned from*lookup_vector*.

The following examples demonstrate two simple Lookup formulas in action.

Let's say, you have a list of sellers in column D (D2:D5) and the products they sold in column E (E2:E5). You are creating a dashboard where your users will enter the seller's name in B2 and you need a formula that would pull a corresponding product in B3. The task can be easily accomplished with this formula:

`=LOOKUP(B2,D2:D5,E2:E5)`

To better understand the arguments, please have a look at this screenshot:

If your source data has a horizontal layout, i.e. the entries reside in rows rather than columns, then supply a one-row range in the *lookup_vector* and *result_vector* arguments, like this:

`=LOOKUP(B2,E1:H1,E2:H2)`

In the second part of this tutorial, you will find a few more Excel Lookup examples that solve more complex tasks. In the meantime, please remember the following simple facts that will help you bypass possible pitfalls and prevent common errors.

- Values in
*lookup_vector*should be sorted in**ascending order**, i.e. from smallest to largest or from A to Z, otherwise your Excel Lookup formula may return an error or incorrect result. If you need to do lookup on**unsorted data**, then use either INDEX MATCH or OFFSET MATCH. *Lookup_vector*and*result_vector*must be a**one-row**or**one-column**range of the same size.- The LOOKUP function in Excel is
**case-insensitive**, it does not differentiate uppercase and lowercase text. - Excel LOOKUP works based on
**approximate match**. More precisely, a Lookup formula searches for exact match first. If it cannot find the lookup value exactly, it looks up the**next smallest value**, i.e. the largest value in*lookup_vector*that is less than or equal to*lookup_value*.For example, if your lookup value is "5", the formula will search it first. If "5" is not found, it will search "4". If "4" is not found, it will search "3", and so on.

- If
*lookup_value*is**smaller**than the smallest value in*lookup_vector*, Excel LOOKUP returns the #N/A error.

The array form of the LOOKUP function searches the specified value in the first column or row of the array and retrieves a value from the same position in the last column or row of the array.

The array Lookup has 2 arguments, both of which are required:

LOOKUP(lookup_value, array)

Where:

**Lookup_value**- a value to search for in an array.**Array**- a range of cells where you want to search for the lookup value. The values in the first column or row of the array (depending on whether you do V-lookup or H-lookup) must be sorted in ascending order. Uppercase and lowercase characters are deemed equivalent.

For example, with the seller names located in the first column of the array (column A) and order dates in the last column of the array (column C), you can use the following formula to search the name and pull the matching date:

`=LOOKUP(B2,D2:F5)`

Note. The array form of the Excel LOOKUP function should not be confused with Excel array formulas. Although it operates on arrays, LOOKUP is still a regular formula, which is completed in the usual way by pressing the Enter key.

- If
*array*has**more rows than columns**or the same number of columns and rows, a Lookup formula searches in the first column (horizontal lookup). - If
*array*has**more columns than rows**, Excel LOOKUP searches in the first row (vertical lookup). - If a formula can't find the lookup value, it uses the
**largest value**in the array that is less than or equal to*lookup_value*. - If the
**lookup value is smaller**than the smallest value in the first column or row of the array (depending on the array dimensions), a Lookup formula returns the #N/A error.

**Important note!** The functionality of the Excel LOOKUP array form is limited and we don't recommend using it. Instead, you can use the VLOOKUP or HLOOKUP function, which are the improved versions to do vertical and horizontal lookup, respectively.

Although there exist more powerful functions to look up and match in Excel (which is the subject of our next tutorial), LOOKUP comes in handy in many situations, and the following examples demonstrate a couple of non-trivial uses. Please note, all of the below formulas use the vector form of Excel LOOKUP.

If you have a column of dynamically populated data, you may want to pick the most recently added entry, i.e. get the last non-empty cell in a column. For this, use this generic formula:

LOOKUP(2, 1/(*column*<>""), *column*)

In the above formula, all arguments except for the column reference are constants. So, to retrieve the last value in a specific column, you just need to supply the corresponding column reference. For example, to extract the value of the last non-blank cell in column A, use this formula:

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

To get the last value from other columns, modify the column references like shown in the screenshot below - first reference is the column to be checked for blank/non-blank cells, and the second reference is the column to return the value from:

In the *lookup_value* argument, you supply 2 or any other number greater than 1 (in a moment, you will understand why).

In the *lookup_vector* argument, you put this expression: 1/(A:A<>"")

- First, you perform the logical operation A:A<>"" that compares each cell in column A with an empty string and returns TRUE for empty cells and FALSE for non-empty cells. In the above example, the formula in F2 returns this array: {TRUE;TRUE;TRUE;TRUE;FALSE...}
- Then, you divide the number 1 by each element of the above array. With TRUE equating to 1 and FALSE equating to 0, you get a new array consisting of 1's and #DIV/0! errors (the result of dividing by 0), and this array is used as
*lookup_vector*. In this example, it's {1;1;1;1;#DIV/0!...}

Now, how it comes that the formula returns the last non-empty value in a column, given that *lookup_value* does not match any element of *lookup_vector*? The key to understanding the logic is that Excel LOOKUP searches with approximate match, i.e. when the exact lookup value is not found, it matches the next biggest value in *lookup_vector* that is smaller than *lookup_value*. In our case, *lookup_value* is 2 and the largest value in *lookup_vector* is 1, so LOOKUP matches the last 1 in the array, which is the last non-empty cell!

In the *result_vector* argument, you reference the column from which you want to return a value, and your Lookup formula will fetch the value in the same position as the lookup value.

Tip. If you wish to get the **number of the row** holding the last value, then use the ROW function to retrieve it. For example: `=LOOKUP(2,1/(A:A<>""),ROW(A:A))`

If your source data is laid out in rows rather than columns, you can get the value of the last non-empty cell using this formula:

LOOKUP(2, 1/(*row*<>""), *row*)

In fact, this formula is nothing else but a slight modification of the previous formula, with the only difference that you use the row reference instead of the column reference.

For example, to get the value of the last non-empty cell in row 1, use this formula:

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

The following screenshot shows the result:

With just a little creativity, the above formula can easily be customized for solving other similar tasks. For instance, it can be used to get a value associated with the last instance of a specific value in a row. This may sound a bit obscure, but the following example will make things easier to understand.

Assuming you have a summary table where column A contains the seller names and subsequent columns contain data of some kind for each month. In this example, a cell contain "yes" if a given seller has closed at least one deal in a given month. Our goal is to get a month associated with the last "yes" entry in a row.

The task can be solved by using the following LOOKUP formula:

`=LOOKUP(2, 1/(B2:H2="yes"), $B$1:$H$1)`

The formula's logic is basically the same as described in the first example. The difference is that you use the "equal to" operator ("=") instead of "not equal to" ("<>") and operate on rows instead of columns.

The following screenshot demonstrates a result:

In all of the Lookup formulas we've discussed so far, the *lookup_vector* and *result_vector* arguments were represented by range references. However, the syntax of the Excel LOOKUP function allows supplying the vectors in the form of a vertical array constant, which enables you to replicate the functionality of nested IF with a more compact and easy-to-read formula.

Let's say, you have a list of abbreviations in column A and you want to replace them with full names, where "C" stands for "Completed", "D" is "Development, and "T" is "Testing". The task can be accomplished with the following nested IF function:

`=IF(A2="c", "Completed", IF(A2="d", "Development", IF(A2="t", "Testing", "")))`

Or, by using this Lookup formula:

`=LOOKUP(A2, {"c";"d";"t"}, {"Completed";"Development";"Testing"})`

As shown in the screenshot below, both formulas yield identical results:

Note. For an Excel Lookup formula to work correctly, the values in *lookup_array* should be sorted from A to Z or from smallest to largest.

If you are pulling values from a lookup table, then you can embed a Vlookup function in the *lookup_value* argument to retrieve a match.

Assuming the lookup value is in cell E2, the lookup table is A2:C7, and the column of interest ("Status") is the 3^{rd} column in the lookup table, the following formula does the job:

`=LOOKUP(VLOOKUP(E2, $A$2:$C$7, 3, FALSE), {"c";"d";"t"}, {"Completed";"Development";"Testing"})`

As demonstrated in the screenshot below, the formula retrieves the project status from the lookup table and replaces an abbreviation with the corresponding word:

Tip. If you are using Excel 2016 as part of an Office 365 subscription, you can use the SWITCH function for similar purposes.

I hope these examples have shed some light on how the LOOKUP function works. To better understand the formulas, you are welcome to download these Excel Lookup examples. In the next tutorial, we will discuss a few other ways to do lookup in Excel and explain which Lookup formula is best to be used in which situation. I thank you for reading and hope to see you on our blog next week!

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