# How to Create a Lag Function in Google Sheets

There does not exist a LAG function in Google Sheets to calculate lagged values, but you can easily calculate lagged values by using the OFFSET function instead.

The following examples show how to use the OFFSET function to calculate lagged values in practice.

## Example 1: Calculate Lagged Values in Google Sheets

Suppose we have the following dataset in Google Sheets that shows the total sales made by some store in 10 consecutive days:

We can use the following formula to calculate the lagged sales values in a new column:

```=OFFSET(B3, -1, 0)
```

We can type this formula into cell C3 and drag it down to every remaining cell in column C:

The “Lag Sales” column shows the sales for a lag of n=1.

For example, on day 2 the store made 17 sales. The lagged value of sales on day 2 (e.g. the sales made on day 1) is 13 sales.

Note: To calculate the lagged value for a different number of previous periods, simply change the -1 in the OFFSET formula to a different number.

## Example 2: Calculate Lagged Values by Group in Google Sheets

Suppose we have the following dataset in Google Sheets that shows the total sales made by two different stores during 5 days each:

We can use the following formula to calculate the lagged sales values by store in a new column:

```=IF(A3=A2, OFFSET(B3, -1, 0), "")
```

We can type this formula into cell C3 and drag it down to every remaining cell in column C:

This function first checks if the store value in the current row is equal to the store value in the previous row.

If it is, then it returns the lagged sales value. If it’s not, then it returns a blank.

For example, in row 3 the sales value was 17. Since the store value in row 2 is equal to row 3, the lagged value of sales is calculated as 13.

However, in row 7 the value for store does not match the value for store in row 6, so a blank value is returned instead of a lagged sales value.

Note: You can find the complete documentation for the OFFSET function in Google Sheets here.