Today, lets learn OFFSET formula.
What is OFFSET and why bother using it?
OFFSET formula gives us reference to a range, from a given starting point with given height and width in cells.
OFFSET formula syntax
OFFSET formula looks like this:
=OFFSET(starting point, rows to move, columns to move, height, width)
- Starting point: This is a cell or range from which you want to offset
- Rows & columns to move: How many rows & columns you want to move the starting point. Both of these can be positive, negative or zero. More on this below.
- Height & width: This is the size of range you want to return. For ex. 4,3 would give you a range with 4 cells tall & 3 cells wide.
And yes, All the arguments to OFFSET can be references to other cells. That means, you can write =OFFSET(A1,D1,D2,D3,D4) which will refer to a range
- Starting from A1
- Offset by D1 rows & D2 columns
- having the size of D3 rows & D4 columns
See below examples to understand the formula better.
OFFSET formula examples
Why use OFFSET?
Why not write a reference like A1:C4 directly?
Here are a few reasons why,
- Dynamic ranges: Reference like A1:C4 always refers to the range A1:C4. ie it is static. But sometimes, we want our ranges to be dynamic. This is required because our data is changing (every month new row is added, every time we launch a product new column is added etc.)
- We don’t know the exact address: Sometimes, we don’t know what our ranges actual address is. Rather, we just know it is starting from a certain cell etc. In such situations OFFSET is useful.
Understand OFFSET formula – Interactive Workbook
Since OFFSET formula is somewhat tricky to get, I created an interactive workbook so that you can understand how it works. When you input all the 5 parameters, the workbook highlights the range that your OFFSET will give. After playing with it for a few minutes, you will understand the formula better.
Practical use for OFFSET – Average of latest week
Lets say we monitor quality of a plant producing purple puppets. One of the KPIs we monitor is % of rejected puppets. We have been tracking the % of rejects by day in a spreadsheet that looks like this:
So how do we calculate average of latest week?
Assuming the values are in range C3:C18, we can write =AVERAGE(C12:C18)
BUT, WE NEED TO CHANGE THIS FORMULA EVERYDAY!!!
Even puppets would find that boring.
By using the OFFSET awesome sauce, we can write the AVERAGE formula once and forget about it.
Lets break-apart this formula and understand
- To calculate latest week’s average, we need to go all the to the last data point and then get 7 rows from it and average those values.
- This is where COUNTA(C3:C300) – 7 comes in to picture. It counts how many values are there in column C and then subtracts 7 from it.
- The OFFSET would then starting point from C3 to latest week’s starting point.
- To know how this formula works, watch below demo.
While offset formula can return with a dynamic range when you beckon, it does have few limitations:
- OFFSET formula is volatile: In plain English it means, whenever there is any change in your workbook, OFFSET formula is recalculated, thus keeping Excel busy a tiny bit longer. This is not an issue if you use OFFSET formula in a small workbook. But when you use lots of OFFSET formulas in large workbooks, you will end up cursing Excel as it takes too much time to recalculate.
- OFFSET formulas are tricky to debug: Because the references are dynamic, debugging a workbook with lots of OFFSETs can get tricky quickly.
Alternatives to OFFSET formula
There 2 fine alternatives to OFFSET formula.
- Use Excel Tables: Since Excel 2007, we can create tables from structured data and write formulas, create charts that refer to dynamic ranges with ease. Click here to know more about tables.
- Use INDEX formula: Although not exactly same as OFFSET, INDEX formula can also be used to generate dynamic range references. Plus, INDEX is a non-volatile formula, so it wont keep Excel busy unnecessarily. Know more about INDEX formula.
Do you use OFFSET formula?
For most of my dynamic range needs, I rely on tables or INDEX formula. I use OFFSET formula when I have to calculate values like average of latest week. In such cases OFFSET is an elegant solution.
What about you? Do you use OFFSET formula? In which situations do you use it? Please share your tips & examples with us using comments.
Know More about OFFSET
Check out below examples to understand OFFSET formula better:
- Calculations: Sum of values between 2 dates | Moving averages | Average of closest numbers| More…
- Modeling: Calculate IRR of dynamic ranges | Manage scenario analysis
- Charting & Dashboards: Dynamic range charts | Top x chart | Analyzing large datasets | KPI dashboards
- Validations & Pivots: Dynamic Data Validation | Dependent Drop downs | De-duplicate & Sort data
- And many more uses of OFFSET