Do you know that we can easily calculate the critical path for a project using Excel formulas?
For a long time, it has been tricky to calculate the Critical Path using Excel formulas. But thanks to the arrival of new Dynamic Array functionality in Excel, we can now calculate critical path. In this article let me describe the approach with an example.
Put on your hardhats, this one is going to blow your minds.
What is Critical Path Method (CPM)?
Critical Path Method gives us a framework to analyze and optimize a project plan. Let’s say you have a project with 6 activities, as depicted below. Then we can find a critical path that determines the total duration of the project using Critical Path Method.
The critical path is the longest sequence of tasks that must be completed to execute a project. The tasks on the critical path are called critical activities because if they’re delayed, the whole project completion will be delayed.
How do you calculate the Critical Path?
To calculate the critical path, you need below details about the project plan:
- Complete list of all planned activities
- Estimated duration for all activities (t)
- Dependencies for each activity
In many real-world scenarios, accurately listing all three of them is impossible. And that is why CPM technique is often criticized.
Once you have all of them, we need to apply critical path algorithm to calculate below 5 values.
- Earliest Starting time (ES): This is maximum Earliest Finish (EF) of all predecessors of an activity.
- Earliest Finish time (EF): This is ES + duration of the activity (t)
- Latest Finish time (LF): This is the minimum Latest Start time (LS) of all successors of an activity.
- Latest Starting time (LS): This is LF – duration of the activity (t)
- Float or Slack (F): This is the gap between Latest Start (LS) and Earliest Start (ES). For activities on critical path this value would be 0.
Learn more about Critical Path Method:
Critical Path Calculations with an Example
Let’s go back to our 6 activity project. We can assign durations for each activity like this:
We can use below notation when capturing this data in Excel table.
Calculating ES, EF, LS, LF & Float with Formulas
Adjacent to the input data table, add 6 columns for all our calculations. Our table should look like this:
Now, lets understand the formulas for Successors, Early Start (ES), Early Finish (EF), Latest Start (LS) and Latest Finish (LF).
Early Start Formula (ES)
Early Start is the earliest an activity can begin. An activity can only start when all of its predecessors have finished. So this is same as the maximum of Early Finish (EF) for all the predecessors. If an activity has no predecessors, then it can start right away.
As we have the list of predecessors in the cell [@Predecessors], we can loop thru them and find the maximum finish time for them.
Here is the formula I used.
=IF([@Predecessors]="",0, MAX(CHOOSEROWS([EF],TEXTSPLIT([@Predecessors],",")+0)))
For activities without predecessors, we set the value of ES as 0.
For all other activities, we split the [@Predecessors] by comma (using TEXTSPLIT) and convert these text values to numbers (by adding a 0 to them). We then pick the maximum of all these activity’s earliest finish time [EF] using MAX & CHOOSEROWS functions.
Early Finish Formula (EF)
This is easy. We just add duration to early start (ES).
=[@ES]+[@[Estimated Duration]]
🤔Did you notice the circular nature of these formulas?
Even though ES formula depends on EF and EF formula depends on ES (head hurts, innit?), you need not worry. Excel will calculate both of these values fine as long as there are no loops in your project data (ie. Activity 1 depends on 2 and 2 depends on 1)
Successors Formula
Before we calculate the Latest Start (LS) and Latest Finish (LF) times, it is a good idea to calculate the list of successors for each activity.
I used this formula for that:
=TEXTJOIN(",",TRUE,FILTER([ID],IFERROR(BYROW([Predecessors],LAMBDA(a, OR(TEXTSPLIT(a, ",")+0=[@ID]))),FALSE),""))
How it works?
For each activity, the list of successors is defined as all the activities that begin immediately after that activity.
So for example, going back to our image of project plan (see below),
the list of successors for activity 1 is {2,3}
To obtain this list for a given activity x:
- We need to filter all the activities
- where x is one of the predecessors
We can use a cocktail of FILTER(), BYROW(), LAMBDA() and TEXTSPLIT() for this.
Here is the basic approach:
- We filter the [ID] column
- by checking for each row (hence BYROW)
- if the [Predecessor]s has the [@ID]
- To perform the check, we first split the predecessors using TEXTSPLIT
- and then compare if any of them equal to [@ID]
- At the end of this BYROW looping, we end up with either TRUE or FALSE values against each [ID]
- After filter fetches all the successors, we just apply TEXTJOIN to combine them to a list. For ex: 2,3
Latest Finish Formula (LF)
Latest Finish (LF) is defined as the latest an activity can finish without derailing the project.
For the activities without any successors, this is same as EF.
For all other activities, we look for the minimum (earliest) LS value of all it’s successors.
Here is the formula:
=IF([@Successors]="",[@EF],MIN(CHOOSEROWS([LS],TEXTSPLIT([@Successors],",")+0)))
How this formula works?
If an activity has no successors (ie it is last activity in the project diagram) we set LF as EF.
For all other activities, we split the [@Succssors] by comma (using TEXTSPLIT) and convert these text values to numbers (by adding a 0 to them). We then pick the minimum of all these activity’s Latest Start time [LS] using MIN & CHOOSEROWS functions.
Latest Start Formula (LS)
This is Latest Finish (LF) minus Duration (T)
=[@LF]-[@[Estimated Duration]]
Float (or Slack)
Now that we have all the calculations done, we can figure out the float (or slack) for each activity. This is the difference between Latest Start (LS) and Earliest Start (ES) for an activity.
=[@LS]-[@ES]
Findout out which activities are on Critical Path
Any activity with ZERO (0) float is on the critical path. It means, there is no wiggle room for that activity.
We can use Excel’s conditional formatting feature to visually identify all such activities.
- Select the table and add a new conditional formatting rule (formula based)
- Use the rule float_column=0 and set the necessary formatting. (see my rule in the below screenshot).
Here is my final project plan table with critical path activities identified.
Critical Path Analysis with Excel - FREE Template
Please download my FREE Critical Path Analysis Template and use your own data to calculate the critical path automatically.
Critical Path Calculations in Excel - Watch the Video
Still confused about these calculations? I made a video explaining the CPM concept & Excel formulas. Check it out below or on my YouTube Channel.
More on Project Management using Excel
If you are a project manager, you are going to love my site. I have articles & templates on all aspects of Project Management. Check them out below:
- Interactive Gantt Chart Template with Excel
- Quick & easy Gantt Chart in Excel
- Project Timeline Chart with Excel
- Project Management Dashboard with Excel
- Project Portfolio Dashboard with Excel
- Complete Project Management Template Pack (Excel)
33 Responses to “Show Months & Years in Charts without Cluttering”
Very CooOOOoool 🙂
Would it work if I merely change the display format for the dates, or do they actually need to be retyped in that format (Nov, Dec, etc)?
ps- it's only about 34 donuts per month, or slightly more than 1 per day. Yum!
To make it work automatically when you create a chart, delete the labels above the Year and Month columns, but keep the label above the Y data (Donuts). The blank cells tell Excel that the first row and first two columns (indicated by the blanks) are special, so it uses the first row for series names an the first two columns for X axis labels.
This is better than the other kind of donut chart, but you'll soon be carrying a big donut around your midsection.
First off, thank you Chandoo for being respectful and taking out the "Jesus" comment. Not that I'd threaten to kill you, or start world-wide riots, or make you go into hiding if you didn't (as OTHERS would; wink, wink, nudge, nudge)... I just really appreciate your respectulness and consideration; so thank you. I was meaning to write you about it, but when I came to your site you'd already made the edit... so again, thank you!
Secondly, I wanna say I think there's an easier way to do what you are demonstrating. I've got a pivot chart with months of data and all I had to do was right-click the x axis and then select "format axis", under "Axis Options" there's a check-box that says "Multi-level Category Labels". The chart I was able to do this on was a pivotchart however so maybe it wouldn't be that easy for a non-pivotchart.
Anyway, love the site. Keep up the good work. Thanks also for being so open about your success, it's very encouraging and motivating.
God (aka Jesus) Bless. 🙂
Hi Chandoo - great site! Another option to save space is to simply rotate the orientation of the text by 90 degrees, so the dates read vertical rather than horizontal. However, I like the elegance of your solution also.
Hey Chandoo -- Great tip. Only yesterday I was working through some strange behaviour with formatting dates in PivotCharts. Seems the axes never want to cooperate. This is a neat and elegant solution I hadn't thought of using. May need to abandon pivotcharts to use formulas like that, but if we use dynamic named ranges, no big sacrifice.
BTW, whatever did you do to get your site blocked in China? Never heard of regime change by a grass-root spreadsheet movement. Maybe your ISP is hosting some problem sites. Chandoo.org is certainly worth it for me to fire up the VPN, but I'm sure you would lose a lot of other visitors from the middle kingdom.
Chandoo ... pls help.. the link is blocked over here... pls can you put the regular link... 🙂
@JP... Excel Axis formatting is linked to cell formatting by default. So you can just have the dates which are formatted to look like months (mmm).
@Erin: It was not my intention to mock anyone's faith or religion. I just used the word as it is quite common. I decided to remove it as I got 2 emails from readers requesting for the same.
Also, the pivot charts take pivot table groupings by default, so you need not do any of the above while making charts from pivot tables.
@Kein: I am not sure why Chinese authorities decided to block my site. I wish they would actually look at the content instead of blocking sites based on simple text matching rules.
@Kapil: The file is mirrored here: http://chandoo.org/img/d/date-axis-months-years-trick.xls
Cool, really cool...
Nice one Chandoo,
Also would like to mention abt useful method while creating dynamic charts.
In any chart where in the months keep on adding - instead of changing the range for the chart every time we add a month, we can actually format the months as dates (probably 1st of every month) still keep the format as "mmm" AND while selecting the data, we can select a huge rows (date column) once and for all, and the chart adjusts automatically with the data that we entered. So next month when I enter Dec's data, I need not change the source data of the chart, however it automatically adjusts.
Hope I made sense.!
Regards,
SS
Thanks, Chandoo! This is a great tip - one that I will definitely put to use. I typically have an axis with mmm yy format, aligned vertically, but this will definitely look a bit cleaner (except in cases where the chart is too small for the axis labels to be displayed horizontally, even without the mmm yy on one line). Thanks again!
Tom
Chandoo,
Thank you for the posts you are very diligent not to mention very helpful. I would like to know how to get the separation lines on the axis? For example your candy sales chart has longer lines separating east and west how do you format that?
Thanks for being very awesome!
-Josh
Hi Chandoo, we can look the formulas because there is a message:"Unsupported features".
Could you send a diferent Link ?
Thanks.
@SS But what if you've got formulas in the data block (i.e where you would enter static data for the month of december)? My chart now shows #N/A #N/A in the axis with no data for all future dates.
Chandoo, I've got a dynamic range set up showing #N/A errors for future dates. The MMM-DD date format format in row works fine, but when I use YYYY and MMM in two rows, the axis shows #N/A #N/A for all future dates with no data. How would you go about keeping those future months hidden?
Matt -
In order for the axis to automatically extend to the dates within the range and ignore #N/A at the end, you need a date-scale axis, and for this you need to use one column with the complete date, not two columns with year and month.
If you want to use two columns, you need to generate Names in the worksheet which define ranges only as long as the number of months. I have a review of dynamic chart approaches in http://peltiertech.com/WordPress/dynamic-chart-review/ and a whole category on my blog at http://peltiertech.com/WordPress/category/dynamic-charts/. Chandoo also has examples of his own on this site.
How do you make a dynamic chart out of this?
I can't get the axis labels range right.
I tried something like this:
=OFFSET(REPORT!$H$10:$I$10;0;0;COUNTA(REPORT!$H$10:$I$100);1)
Any idea?
Ethan -
Your offset formula defines a range 1 row in size, but the technique here requires 2 rows. Your definition should end with
;2)
instead of
;1)
Thanks Jon,
Got it working now
Great! Now, is there any way to do this directly in Powerpoint? I don't like having linked excel files, so I create the graphs right inside Powerpoint, any way to do this there? I tried and was unsuccessful.
Thanks.
Cool tip Chandoo......thanks
[...] extract year and month from dates to avoid a mess in our stock chart. Chandoo has a great post: Show Months & Years in Charts without ClutteringIn cell B2:=YEAR(D2)In cell B3:=IF(YEAR(D3)=YEAR(D2), "", YEAR(D3))Cell C2:=IF(TEXT(D2, [...]
Hi there,
I have got a data ranging for 3 years. I want to show a chart which shows Jan of 2011, 2012 and 2013 together side by side; then Feb11, Feb12 and Feb13 side by side, then Mar11, Mar12 and Mar13, and so on until December.
Please help. Thanks.
@Bilal
Do you want a number of charts next to each other as separate charts or the data next to each other in a single chart?
What type of chart were you thinking about?
Can you post your data for us to review?
Refer upload instructions at: http://chandoo.org/forum/threads/posting-a-sample-workbook.451/
Hi there
Very good solution this. I have another question on it, though. How do you format the X-axis with monthly gaps (ie, with labels "Jan 2012", "Apr", "Jul", "Oct", "Jan 2013", "Mar", etc), when you're dealing with a data series with weekly or daily data points? The Axis Options dialogue box doesn't appear to offer "Date axis" as an option under the "Axis Type" section.
I've managed to do it in one case with weekly data by setting the interval between tick marks at 13 -- the approximate number of weeks in a quarter -- to get 3-month intervals. But this wouldn't work if I wanted to show 1-month intervals, or had a more detailed daily data series to work with.
Any luck getting the dates to work on a scatter graph? I'm only getting numbers. Works fine on line graphs though.
How can we do the vice versa? i.e. on the x-axis showing year on the level 1, and months on level 2.
I wanted to build these kind of axis labels for 5 years, with year on top and months at the bottom, but it should form in such a way that the seperating lines should seperate the entire data set only at December of each year, and no lines in between any month.
@Apoorve
Just re-arrange the columns
You need to put a space in all cells where you don't want a year
See the attached file
http://chandoo.org/wp/wp-content/uploads/2010/11/Chart-for-Apoorve.xlsx
Unfortunately you don't get any control over lines its all or nothing.
Hello - the link seems to be broken:
http://cid-b663e096d6c08c74.office.live.com/view.aspx/Public/date-axis-months-years-trick.xls
Regards.
Like!!
Three times already today I have used this website and saved a ton of work time in researching excel tricks.
Suggestion: Why not have a "like" or "this article was useful to me" button. That way you can see what is most useful by your users and maybe generate more content based on those "likes".
Just saying. Thanks again and you're doing a great job!
Thanks for the tip. However, I couldn't download your file. The link is broken.
Thank You for taking the time to post this tip. I hope that you have a blessed day.
The link does not work properly and I'm not sure how to actually get the graph to display like this, its frustrating me a tonne. I cant work out what to google either to find an answer elsewhere! 🙁
Is this possible with waterfall chart. Data hereunder -
Years Abbrevation Amt
2020 BEG 2,006
REV 1,950
EMP 1,058
DM (3,244)
OOE 1,078
OPMT 182
AB (638)
END 2,392
2021 REV 8,534
EMP 67
DM (2,142)
OOE (3,120)
OPMT 510
AB 1,008
END 7,249