12 Rules for Making Better Spreadsheets

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Larry sent me a list of 12 beautifully defined rules for making better spreadsheets with this comment:

I thought I would share with you a set of “rules” for building spreadsheets. I developed these over many years of financial analysis and reviewing the work of other analysts.

12 Rules for Making Better Spreadsheets

His rules are not only comprehensive, but valid for all types of spreadsheets, not just financial models. Here is the complete list:

  1. Most important rule: never start a spreadsheet without first being able to define in one sentence or less why you are creating the spreadsheet.
  2. Second most important rule: a spreadsheet should explain itself. Six months from now, someone else will not be able to tell what you were thinking when you created the spreadsheet. You may not even remember your own thoughts as to why you created it. A well-defined spreadsheet should justify its own existence.
  3. Every spreadsheet should have a title. This should help explain “second most important rule” and allow the reader to understand what they are looking at.
  4. The footnote section of a spreadsheet should include the path/filename/date and creator’s name.
  5. Audit trail: whenever possible, formulas should be used in the spreadsheet rather than inputting numerical values. This way you, or someone else, can follow the logic of the spreadsheet.
  6. Assumptions: mathematical assumptions should be identified in separate cells, not buried within formulas. That way they can be printed out as required. It is very easy to forget that you have a formula that says (C5 X 200). If instead, it says (C5 X D7) and then D7 shows 200, it is less likely to forget what assumptions are included in the spreadsheet.
  7. Assumptions: document your assumptions. If you’re increasing a value by an inflation rate, make note that this is an inflationary increase. A few words to the right hand side of a cell can save many hours of hunting and digging at a later date.
  8. Unless your data source is obvious, you should document where you obtained your data. A few words to the right hand side of a cell can save many hours of hunting and digging at a later date. (Yes, you read that in the last bullet as well).
  9. Presentation format: all spreadsheets, should be designed so that it is easy to follow the process flow and result. Almost every spreadsheet should be presentable and understandable to senior management without additional formatting or explanation. (tips: how to design boss-proof excel sheets)
  10. It is okay to add notes, procedures steps or other explanations in text format within your spreadsheet. Any guidelines provided to the next person who looks at or works on the spreadsheet will be highly appreciated.
  11. Learn to use the intermediate level functions within Excel. These include: sum, sumif, macro’s, logic (if, then, else), auto sum, filtering, auto subtotal, sorting, charting, pivot tables, auto formatting, conditional formatting and formula auditing. None of these functions are at advanced level or particularly difficult. If you need help on how to use them; please ask someone else in the department, use the Excel help function, or look up the function on the web. The use of these functions will save you a great deal of time and make your spreadsheets more accurate.
  12. Do the common sense test. Look at the spreadsheet as though you didn’t create it. Does it answer the question asked? Can you follow the logic? Does the result seem OK? If all this is yes, then ask what decision will be made from knowing this information. If you can’t answer this, go back to step one.

If we summarize all these rules in one sentence, it will be,

Your spreadsheet should have a purpose, it should be well documented & easily understandable and you should make use various features in Excel to achieve this.

Rules for Better Spreadsheet - PosterDownload Larry’s Rules for Better Spreadsheets Poster:

I took the liberty of putting all these 12 rules in small poster. Take a print and stick near your workspace to remind you how to make better spreadsheets.

Download it here [PDF].
Financial Modeling using Excel - Online Classes by Chandoo.org & Pristine

Additional Material on Making Awesome Spreadsheets:

Thank you Larry

Thank you so much for sharing these rules with all of us Larry. I am sure our readers are going to dig this one 🙂

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15 Responses to “Compare 2 Lists Visually and Highlight Matches”

  1. Nunes says:

    Hi,
    I solved this in a little different way.

    We have 2 lists, one starts at A1 and other at B1, both are vertical arrays.

    First thing is define 2 named ranges, list1 and list2:
    list1 refers to "=OFFSET(Sheet1!$A$1;0;0;SUMPRODUCT(--(Sheet1!$A$1:$A$1000""));1)"
    list2 refers to "=OFFSET(Sheet1!$A$1;0;0;SUMPRODUCT(--(Sheet1!$B$1:$B$1000""));1)"

    this way lists will be dynamically sized when you had or remove elements (you can't have blanks and you can't have more than 1000 elements).

    Then I use conditional formatting in column A when this formula is true:
    "=NOT(ISERROR(MATCH(A1;list2;0)))"
    and "=NOT(ISERROR(MATCH(B1;list1;0)))" to list2.

    This way we eliminate the need for auxiliary columns or lists.

    Hope you like my way! 😀

    Nunes

  2. glw says:

    Simple conditional formatting formula.
    Assuming lists vertical lists starting in A1 & B1
    To highlight just one column (assume B for example)
    Conditional formatting>New Rule>by formula
    =MATCH(B1,$A$1:$A$99,0)
    Set the cell fill to what ever color you prefer & press OK

    To highlight both columns repeat with this formula for cell in column A
    =MATCH(A1,$B$1:$B$99,0)

    This approach doesn't require named fields or addtl columns
    glw

  3. Alan says:

    Say I had 1 list in A2:A20 and another in B2:B20.

    To format all the items in column A that are repeated in column B I would use the following Conditional Formatting rule.

    =IF(ISNA(VLOOKUP(A2,$B$2:$B$20,1,false)),true,false)

    All the duplicates are highlighted. It us a very simple example of comparison.

  4. Lee says:

    I may be missing something here, but I usually highlight both my lists by holding ctrl eg A1:A20 E10:E40 then choose conditional formatting from the ribbon and then highlight duplicates, and this does it?

  5. Greg says:

    Lee, I was perplexed as well. I do the same thing you do with the conditional formating. A drag and click to highlight range and choose highlight duplicates does the trick for me.

  6. Alan says:

    I believe these methods are to check if an item from one list also appears in the other list. So if an item mentioned many times in one list if also mentioned in the other list or not.

    The Conditional Formatting highlight duplicates feature will do this, but it will also highlight an item if it appears multiple times in the one column or list.

  7. i48998 says:

    Hi, I would just like to know (if you are willing to share) which image editing program you use to make your image like above, like they are torn apart from bottom? I've been looking for long.

  8. Hui... says:

    @i48998
    Chandoo is on Holidays, but Chandoo uses Paint.Net
    Paint.net is a free download available at http://www.paint.net/
    .
    I use CorelDraw/PhotoPaint
    .
    We both use the Snipping Tool (a freebe with Win Vista/10)
    .
    We both use Camtasia for doing screen captures to make animated GIFs where you see animation.

  9. Rick says:

    Here is how I would accomplish
    (1) Define Names: List_1, List_2
    (2) =ISNA(MATCH(D4,List_2,0))-1 (Conditional Format formula List_1)
    (3) =ISNA(MATCH(D4,List_1,0))-1 (Conditional Format formula List_2)

    ISNA will return 1 if NO Match and O if Match by adding a -1 will make: NO Match 0 and Match a -1 which is True

  10. Hi all
    this my first Post here
    i think we can take Unique List for tow list to know what is not Duplicate By this Array formula
    =IFERROR(INDEX($D$6:$D$33,SMALL(IF(ISERROR(MATCH($D$6:$D$33,$B$6:$B$33,0)),ROW($D$6:$D$33)-ROW($D$6)+1),ROWS($J$5:J5))),"")
    and this one for Duplicate Value
    =IFERROR(INDEX($D$6:$D$33,SMALL(IF(ISNUMBER(MATCH($D$6:$D$33,$B$6:$B$33,0)),ROW($D$6:$D$33)-ROW($D$6)+1),ROWS($J$5:J5))),"")

    Don't forget to Enter This Formula by Pressing Ctrl+Shift+Enter

  11. Excel Addin says:

    without wanting to ruthlessly self promote here, I do have an addin that does neatly compare two ranges, not just in columns, so you might want to check that out.

    Having said that this is a pretty neat solution if you dont want to be going down the VBA or purchase route. I like it

    however, could you not do something with the remove duplicates feature in Excel 2010 and then compare the resulting data set?

  12. SirJB7 says:

    Hi, Chandoo! I've found yesterday your Excel website... What can I say? It's just awesome, Excellent. Being a developer for 30 years, more than 15 with Office products, and wow!, how many things I discovered in a couple of hours, and what pretty resolved.
    I decided to take the long path of the newbies and read all your examples and write down by myself all of them, and when I arrived to this (the comparison of two lists) I think I've found a problem:
    a) in "Step 4: Apply conditional formatting to Second List - Use the same logic, but this time the rule becomes =COUNTIF(count1s,$H6)" it should say "Step 4: Apply conditional formatting to Second List - Use the same logic, but this time the rule becomes =COUNTIF(count1s,$H6)>0", but this is a typing error that I believe all of us here might have discovered and corrected
    b) the very problem: I wrote down two different lists, in different ranges, and with different number of elements, I specified the equivalent conditional formats, et non voilá!, I didn't get what expected. So I downloaded your example book, I checked range names, formulaes, conditional formats and all OK. So I copied -just values- from my book to yours, and I still couldn't achieve the goal.
    I'm using Excel 2010 in spanish, I'm from Buenos Aires (Argentina), and my book is at your disposition whenever you considerate it appropiate.
    Thanks in advance for your time, and again my congratulations for your work here.
    Best regards.
    SirJB7

  13. SirJB7 says:

    Comparison of 2 lists visually with highlights
    Author: SirJB7 / Date: 11-Dic-2011
    Pros: no duplicated tables, no matrix formulaes, no named ranges, no VBA code, just conditional formatting
    Cons: not found yet, comments and observations welcome
    Features:
    a) standard problem: highlights in orange/yellow elements existing in the other list
    b) optimized problem: idem a) plus highlights in red/violet first occurrence of elements existing in the other list
    Sheet contents:
    a) conditional format, 1 rule per list (2 methods used)
    A1:A20, first list
    B1:B20, second list
    a1) range A1:A20, condition =NO(ESERROR(BUSCARV(A1;B$1:B$20;1;FALSO))), format Orange ---> in english: =NOT(ISERROR(VLOOKUP(A1,B$1:B$20,1,FALSE)))
    a2) range B1:B20, condition =CONTAR.SI(A$1:A$20;B1)>0, format Yellow ---> in english: =COUNTIF(A$1:A$20,B1)>0
    b) conditional format, 2 rules per list (2 methods used)
    D1:D20, first list
    E1:E20, second list
    b1) range E1:E20, condition 1 =Y(NO(ESERROR(BUSCARV(D1;E$1:E$20;1;FALSO)));COINCIDIR(D1;D$1:D$20;0)=FILA(D1)), format Red ---> in english: =AND(NOT(ISERROR(VLOOKUP(D1,E$1:E$20,1,FALSE))),MATCH(D1,D$1:D$20,0)=ROW(D1))
    same range, condition 2 and format 2, same as a1)
    b2) range E1:E20, condition =Y(CONTAR.SI(D$1:D$20;E1)>0;COINCIDIR(E1;E$1:E$20;0)=FILA(E1)), format Violet ---> in english: =AND(COUNTIF(D$1:D$20,E1)>0,MATCH(E1,E$1:E$20,0)=ROW(E1))
    same range, condition 2 and format 2, same as a2)
    Personally I like the a2) and b2) solutions, I think the formulaes are prettier.
    I still don't know the rules of this website and forum, but it any precept is infringed I'm willing to share the workbook with the solution. If it breaks a rule, I apologize and promise that won't happen again.
    Best regards for all!

  14. sunil says:

    Dear All i have a complicated situation...

    1. I have two sheets of data Sheet1 and Sheet2 (from various sources) - Both of these contain data matching and Not matching as well..

    2. Now for me i need to build an excel where in i need to get sheet 3 with values that are present in a column of Sheet 1.

    What ever Sheet 1 doesn't have i dont want those rows from sheet 2 to be populated into Sheet3.

    Can any one help me out.

  15. Jagdev says:

    Hi Team

    The above example is to compare partial name from 2 different columns.

    If I want to cross check it in a single column. I have both correct and partial correct/match entries in a column. Is there any way I can find both the entries in the column.

    Regards

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