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.
=AVERAGE(OFFSET(C3,COUNTA(C3:C300)-7,0,7,1))
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.
OFFSET limitations
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
13 Responses to “Gantt Box Chart Tutorial & Template – Download and Try today”
Hi Chandoo
As one of your students I have followed your detailed example through with great success. However, Excel is acting in an unexpected way and I wonder if you could take a look?
http://cid-95d070c79aef808e.office.live.com/self.aspx/.Public/Gantt%20Box%20Chart.xlsm
On my version, I have to type 40239 (Which equates to 2 Mar 2010) to get the chart to display 31 May 2010 (which should be 40329)!!??
Have I done something wrong or is Excel acting up?
Thx
Oli
PS Your example file in 2007 displays correctly.
Hi,
I like this idea a lot, but I agree the name is a little drab.
As an American I may just be seeing things, but to me the combination of lines and bars on your chart looks like a bunch of cricket bats.
Maybe you could work that into a catchier name. 🙂
Cheers!
Here is some code I use to keep the axis synched.
It may be useful to some of your readers
It is based on a comment I saw on Daily Dose of Excel.
Function SynchGanttAxis(Cname, lower, upper)
'Sets the X min and X max for Category axis
Application.Volatile
On Error Resume Next
'
'Top Horizontal Axis
With ActiveSheet.Shapes(Cname).Chart.Axes(xlCategory, 1)
.MinimumScale = lower
.MaximumScale = upper
End With
'Bottom Horizontal Axis
With ActiveSheet.Shapes(Cname).Chart.Axes(xlValue, 2)
.MinimumScale = lower
.MaximumScale = upper
End With
End Function
Function SynchVerticalAxis(Cname, lower, upper)
Application.Volatile
On Error Resume Next
' Excel 2007 only
'Right hand vertical axis
With ActiveSheet.Shapes(Cname).Chart.Axes(xlValue, 1)
.MinimumScale = 0
.MaximumScale = upper
End With
End Function
@Oli.. Can you check your file again.. I see 40329...
@Dave: Even I saw things.. the bars actually looked like lollipops. How about calling this lollipop chart - now that would be yummy and goes along the tradition of naming charts after eatables (bar, pie, donut...)
@Bob: Superb stuff... thanks for sharing 🙂
Hi Chandoo
This looks really good and I think it can also be applied to show project phases / milestones.
Question: Thinking further could this be amended to display a project lifecycle (Idea through to Implementation say 7 phases) on one bar / row? Just imagine 20 projects within a programme all on one chart one bar each showing their respective lifecycle stages i.e. on one page.
Idea: As the Gantt Box Chart this is quite intensive to set up re formatting etc how about the added extra of once you have completed this to "Save as template" i.e. saves the formatting and layout of the chart as a template so you can apply to future charts. Simple to do and will save the time formatting etc again and again and again.
Therefore tip: Click on your chart demo and then click on Save As template icon (2007) - edit file name and click on save. Ready to use / apply via Templates in Change Chart Type window.
Thanks and be very interested if the lifecycle question can be resolved
Mike
How embarrassing.
I was obviously suffering from numerical dyslexia. I was one of those days.
@Mike H: You can easily make this chart to work like a generic project lifecycle plan chart. All you have to do is,
1. in a separate sheet define the steps of lifecycle and various dates in a table (with 5 columns for each of the projects you have).
2. now use a control cell to input the project name you want to show in the chart
3. based on the input, use OFFSET Formulas to get the correct data
4. Rest is same as the tutorial above
For more info on the dynamic charting visit http://chandoo.org/wp/tag/dynamic-charts/ and http://chandoo.org/wp?s=OFFSET
Your solution is really smart but in the en Excel isn't meant to do stuff like this. I, as a former PM, always thought is was frustrating that you had to do stuff like this for something simple like a Gantt chart. So I built Tom's Planner. And would like to plug it here. I think it really solves the problem you are trying to solve in the most efficient way. Check out http://www.tomsplanner.com for a free account or play around with the demo.
Hi there,
Chandoo - this is really a very nice and helpfull chart - I adopted it, so I can report a forecast or the delay of a certain task (coming from my role as an auditor for projects).
One topic I´m currently struggeling with: I do have a project lasting for lets say 12 month. For a management reporting, I want to have kind of snapshot, lets say one month back and 2 month in the future. I tried with the offset formula, but failed. Any idea?
Thx
Lopi
[...] Ein viel geliebter Klassiker ist die Erstellung von GANTT-Diagrammen mit Excel. Wir hatten das Thema wiederholt schon hier. Chandoo.org hat sich mal wieder mit einer neuen Variante hervorgetan: Das GANTT-Box-Chart. [...]
[...] [...]
Hi Chandoo - fantastic xls. One thing I can't figure out how to do is adjust the alignment of the vertical axis. I would like to left align so that I could indent to represent sub tasks. Can that be done? Or is there a better way?
I've been trying to work out if there's a way to show weekends on the graph. The closest thing I've got is to add them on a secondary axis, but then I haven't been able to keep both axis lined up together! Any ideas?
Following on from this - is it possible to show things like holidays?