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The Good Calculation Guide
Thursday, 03 January 2008
The Top 3 Rules for Good Calculations
1. Be clear about the purpose of the calculation from the outset.
2. Validate your calculation - say how you know it is right.
3. Transparent calculation method - show your working and cite all reference material.
And the Top Ten Excel Tips for Good Calculations
4. Use of consistent systems of units so that it is easy to change between systems (SI and US).
5. Use sketches to explain purpose and charts to provide a graphical response to user input.
6. Use headings to identify each step of the calculation. The flow of the calculation should be from top to bottom. If all calculations are contained in a column it is easy to copy a column to generate a table for sensitivity studies.
7. Separate your work sheet into areas for calculation presentation and ‘scratch’ space (for supporting tabular data or chart series data). Use hyperlinks to navigate between related parts of the calculation. Worksheets should be independent and self contained, so that you can move them from one workbook to another using Excel's Move and Copy worksheet commands.
8. Use of drop down lists (data validation or combo boxes) to read data tables and use of curve fitting data for graphical data.
9. Use Excel comment feature to add instructions on how to use the sheet. Use notes on the page if they are relevant to the calculation method.
10. Use the XLC add-in for validation and transparency of calculation method.
Note: The XLC CalcSheet template features the tips described above and so it is the best way to start a new calculation.

We understand that we cannot be too prescriptive regarding how to set out your calculations and that users often have good reason for not following our advice. Please adopt our recommendations as far as practical. You might even be tempted to share your calculations with the rest of the ExcelCalcs community... Read on.


Why Publish your calculations on ExcelCalcs?
1. FREE SUBSCRIPTION – Emailing your first calculation gives you a free subscription to the site. We want to offer calculations on all subjects so it is our way of thanking you for your contribution. Free XLC Pro Awards are made at the discretion of our site administrators. Here are some ideas for calculation topics or maybe you would like to  discuss an idea with us before starting. Just submit your calculation using the upload link at the bottom of the page.
  • Free 3 Month XLC Pro Subscription for any calculation of interest to the ExcelCalcs community. We welcome calculations on any subject at all. You may already have a suitable calculation stored on your hard drive?
  • Free 12 Month XLC Pro Subscription for any calculation following the principles set out in the ExcelCalcs Good Calculations Guide. We appreciate it is not always possible to follow the guide explicitly but use of the guide helps ensure consistency and quality of calculations.
  • Free Lifetime XLC Pro Subscription it quickly becomes clear that some authors are enthusiastic supporters of the site donating a number of good calculations which they support by replying to user comments. We are only too pleased to offer these users free lifetime XLC Pro subscriptions.
2. SAFE STORAGE – Use “My Calcs” feature to list all your uploads. Never again loose calculations on your hard drive!
3. ENHANCE YOUR CONTENT – we add links and zooming graphic previews to your download. Each download page has easy to copy HTML code to create links and windows to your calculation for inclusion in emails and websites.
4. EASY VERSION CONTROL & DISTRIBUTION - Use the “Update Calcs” link from the download page and the ‘Version History’ button to record reasons for updating the calculation. Anyone subscribed to your calculation will be automatically emailed when the calculation is updated.
5. GREAT USER FEEDBACK –Receive thanks for your work and the opportunity to discuss it using the download page comment feature. The ExcelCalcs community is a professional community who have contributed either financially or by donation of their own work to become members. Their comments are valuable and drive a virtuous quality circle.
6. INCREASE YOUR EXPOSURE – ExcelCalcs ranks amongst the most visited engineering sites and we work to ensure good search engine performance. We allow authors to include links back to their own site.
Some points to note before uploading 7. DON'T REPEAT - Search the repository before you propose a calculation we do not want to repeat ourselves. Any calculation subject is welcome.
8. IDENTIFY ADD-INS - Clearly identify any other Excel Addins that are required.
9. NO PLAGIARISM - Make sure that you own the calculation. We never want to be accused of plagiarism so you must have the right to give us your calculation. If you have been inspired by other authors please give credit where credit is due. 
10. UNPROTECTED WORKSHEETS - Keep worksheets and macros unprotected.
Thank you for donating your calculation to ExcelCalcs.

Upload a new calculation (owned by you, unprotected and not repeating an existing calculation)

Please follow this procedure if you are updating an existing calculation.

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